TRAYNOR, J.
Plaintiffs are engaged in the contracting business in the Los Angeles area. They brought the present action against defendant labor unions and their officers for damages and injunctive relief against strikes allegedly called by defendants.
In their second amended complaint plaintiffs allege that plaintiffs and defendants are parties to a collective bargaining agreement known as the BCA-AF of L Master Labor Agreement. This agreement provides that a contractor shall have complete freedom in hiring workmen, except that he must first call on the local union having jurisdiction over the area in which the contracting work is to be done to satisfy his need for labor. The local union must immediately furnish the required number of competent and skilled workmen, and if after 48 hours notice it has failed to do so, the contractor is free to obtain workmen from any available source. Furthermore, the contractor is permitted to transfer workmen up to 10 per cent of his current requirements in any craft from the jurisdiction of one local union to the jurisdiction of another local union. He may transfer more than 10 per cent if permitted by the constitution and by-laws of the craft at the time the collective bargaining agreement was entered into. The by-laws of the Los Angeles County District Council of Carpenters permit such a transfer up to 50 per cent of a contractor’s requirements, and also require a local union to honor a contractor’s request for specific workmen. The agreement also provides that the unions will not call a strike against a contractor during the life of the agreement, but that all grievances or disputes over the interpretation or application of the terms of the agreement will be settled by a specified grievance procedure and by arbitration.
The complaint further alleges that plaintiffs entered into contracts to do the carpentry work on various construction [52]*52projects in the Los Angeles area. Pursuant to the collective bargaining agreement, plaintiffs called on defendant local unions to supply them with workmen. The workmen sent to plaintiffs were, however, unskilled and incompetent, and furthermore defendants informed plaintiffs that they would not be permitted to transfer workmen from the jurisdiction of one local union to the jurisdiction of another local union in excess of 10 per cent of their current requirements. Defendants also refused to honor plaintiffs’ requests for named workmen or to permit plaintiffs to transfer their regular workmen from different parts of Los Angeles County to specific construction projects. Defendants ordered strikes of plaintiffs’ employees on specific construction projects, and finally brought about a strike of all plaintiffs’ employees.
The complaint alleges that the only reasons defendants gave for their conduct were that plaintiffs are labor contractors and are violating state safety regulations; that in fact plaintiffs are not labor contractors since they undertake to do complete carpentry jobs and not merely to furnish workmen, and that in any event labor contracting is prohibited neither by law nor by the collective bargaining agreement; that a state safety inspector found that plaintiffs were not violating any state safety regulations; and that defendants’ purpose in calling strikes was to harass plaintiffs and totally destroy their business.
Plaintiffs seek to state three causes of action: breach of the collective bargaining agreement through a violation of the no-strike clause, a tortious attempt to destroy plaintiffs’ business without any legitimate labor objective, and a violation of the Cartwright Act (Bus. & Prof. Code, §§ 16700-16758) by restraining trade without any legitimate labor objective. On the basis of the complaint, testimony, and numerous affidavits, the trial court issued a preliminary injunction against defendants’ calling or continuing a strike against plaintiffs, and it is from this order that defendants appeal. In view of our conclusion that the issuance of the injunction was justified by the breach of the collective bargaining agreement, we do not find it necessary to consider the second and third causes of action stated in the complaint.
Defendants first contend that the trial court was without jurisdiction to issue its injunction because the National Labor Relations Board has exclusive jurisdiction over the conduct alleged in the complaint. It is now well established that if conduct may be reasonably deemed to fall within [53]*53the provisions of the Labor Management Relations Act defining unfair labor practices (29 U.S.C. §§ 158(a)-(b)), a state court has no jurisdiction to grant injunctive relief under either state or federal law, even if the National Labor Relations Board has declined to exercise jurisdiction over the controversy. (Weber v. Anheuser-Busch, Inc., 348 U.S. 468, 481 [75 S.Ct. 480, 99 L.Ed. 546]; Guss v. Utah Labor Relations Board, 353 U.S. 1 [77 S.Ct. 598, 1 L.Ed 2d 601]; Charles H. Benton, Inc. v. Painters Local Union, 45 Cal.2d 677, 681 [291 P.2d 13].) The conduct alleged in the present case, however, cannot reasonably be deemed to fall within any of the provisions of section 8(b) of the federal act defining unfair labor practices by unions. (29 U.S.C. § 158(b).)
Conduct that constitutes a breach of a collective bargaining agreement is not for that reason alone an unfair labor practice. Proposals to make breach of contract an unfair labor practice were before Congress when it enacted the Taft-Hartley law, but were specifically rejected by the conference committee on the ground that once the parties had entered into a collective bargaining agreement, enforcement should be left to the usual processes of the law and not to the National Labor Relations Board. (See Association of Westinghouse Salaried Employees v. Westinghouse Elec. Corp., 348 U.S. 437, 443-444 n. 2 [75 S. Ct. 488, 99 L.Ed. 510] (Mr. Justice Frankfurter concurring); Cox and Seidman, Federalism and Labor Relations, 64 Harv. L. Rev. 211, 243-245.)
Defendants contend, however, that the conduct alleged falls within the provisions of section 8(b) (4) (A) (29 U.S.C. § 158(b) (4) (A)), which make it an unfair labor practice for a labor organization “to engage in, or to induce or encourage the employees of any employer to engage in, a strike or a concerted refusal in the course of their employment to . . . perform any service, where an object thereof is . . . forcing or requiring . . . any employer or other person . . . to cease doing business with any other person. . . .” This prohibition contemplates the existence of a primary employer and a secondary employer, and action by the union to induce the employees of the secondary employer to cease performing services for him in order to compel him to stop doing business with the primary employer, the ultimate object of the union’s displeasure. It has no application to the present case since the conduct alleged consisted in calling strikes only of plaintiffs’ employees, and there is no suggestion that employees of other employers, either general contractors or subcon[54]*54tractors, were induced to refuse to perform services. (See International Brotherhood of Elec. Workers v. National Labor Relations Board, 341 U.S. 694, 698-706 [71 S.Ct. 954, 95 L.Ed. 1299]; National Labor Relations Board v. Denver Bldg. & Constr. Trades Council, 341 U.S. 675, 685-690 [71 S.Ct. 943, 95 L.Ed. 1284]; National Labor Relations Board v. International Rice Milling Co., 341 U.S. 665, 670-673 [71 S.Ct. 961, 95 L.Ed. 1277]; National Labor Relations Board v. General Drivers (5th Cir.), 225 F.2d 205, 208-209, cert. denied, 350 U.S. 914 [76 S.Ct. 198, 100 L.Ed. 801].)
The complaint does allege that as a result of defendants’ activities plaintiffs will acquire the reputation of being in labor difficulties, and that general contractors will hesitate to do business with them. Such an effect on secondary employers, however, is always possible when there is a strike of the employees of a primary employer, and is not prohibited by section 8(b)(4)(A). One of the usual purposes of any strike is to make it more difficult for an employer to do business by persuading customers not to deal with him. Section 8(b)(4)(A) permits unions to use such persuasion, whether by direct solicitation of the customers or by indirect pressures of the kind alleged in the present case, so long as pressure is not brought on the customers by inducing strikes of their own employees. (National Labor Relations Board v. Business Machine & Office Appliance Mechanics Board (2d Cir.), 228 F.2d 553, 556-560, cert. denied, 351 U.S. 962 [76 S.Ct. 1024, 100 L.Ed. 1483]; Rabouin v. National Labor Relations Board (2d Cir.), 195 F.2d 906, 911-912.) Defendants’ interpretation of section 8(b) (4) (A) is contrary to the authorities and would change it from a prohibition against secondary strikes and boycotts to a sweeping prohibition against all strikes when an incidental effect is to persuade customers not to deal with an employer.
Sections 8(b)(3) and 8(d) (29 U.S.C. §§ 158(b)(3), (d)) furnish more substantial support for defendants’ contention that the complaint alleges conduct constituting an unfair labor practice. Section 8(b) (3)provides: “It shall be an unfair labor practice for a labor organization ... to refuse to bargain collectively with an employer. . . .” Section 8(d) provides:
“to bargain collectively is the performance of the mutual obligation of the employer and the representative of the employees to meet at reasonable times and confer in good faith with respect to wages, hours, and other terms and conditions [55]*55of employment, or the negotiation of an agreement, or any question arising thereunder, and the execution of a written contract incorporating any agreement reached if requested by either party, but such obligation does not compel either party to agree to a proposal or require the making of a concession: Provided, That where there is in effect a collective-bargaining contract covering employees in an industry affecting commerce, the duty to bargain collectively shall also mean that no party to such contract shall terminate or modify such contract, unless the party desiring such termination or modification—
“(1) serves a written notice upon the other party to the contract of the proposed termination or modification sixty days prior to the expiration date thereof, or in the event such contract contains no expiration date, sixty days prior to the time it is proposed to make such termination or modification;
“(4) continues in full force and effect, without resorting to strike ... all the terms and conditions of the existing contract for a period of sixty days after such notice is given or until the expiration date of such contract, whichever occurs later. ...”
A strike in violation of section 8(d)(4) is an unfair labor practice, and a strike may violate 8(d)(4) whether or not it also breaches a no-strike provision in a collective bargaining agreement. A strike violates 8(d)(4) when the union has not complied with the notice and waiting requirements imposed by the statute, including the requirement that there be no strike before the expiration of the contract or before a time provided in the contract for reopening negotiations. (See National Labor Relations Board v. Lion Oil Co., 352 U.S. 282 [77 S.Ct. 330, 332-336, 1 L.Ed.2d 331].)
All strikes during the life of a collective bargaining agreement, however, are not violations of 8(d)(4). A strike called to protest an employer’s own unfair labor practice, for example, does not violate 8(d)(4) because it is not a strike aimed at terminating or modifying the contract. (Mastro Plastics Corp. v. National Labor Relations Board, 350 U.S. 270, 285-286 [76 S.Ct. 349, 100 L.Ed. 309].) The decision in the Mastro Plastics case, and language in the recent Lion Oil case (77 S.Ct. at 335, and Mr. Justice Frankfurter concurring and dissenting at 338-341), indicate that the prohibition of 8(d) is confined to “bargaining strikes.” Mr. Justice Frankfurter points out, 8 (d) “has no effect on whether [56]*56unions may validly strike over nonbargaining matters.” (77 S.Ct. at 341.) The National Labor Relations Board in its opinion in the Lyon Oil case makes it clear that its decision ‘ ‘ has no bearing on the right to strike for reasons and purposes other than to obtain contract modification or termination. We say only that strikes to alter the provisions of a firm contract of fixed duration . . . must await the termination date.” (Lyon Oil Co., 109 N.L.R.B. 680, 684; see also National Labor Relations Board v. Wagner Iron Works & Bridge Workers (7th Cir.), 220 F.2d 126, 141, cert. denied, 350 U.S. 981 [76 S.Ct. 466, 467, 100 L.Ed. 850]; National Labor Relations Board v. Mastro Plastics Corp. (2d Cir.), 214 F.2d 462, 465-466, aff’d, 350 U.S. 270 [76 S.Ct. 349, 100 L.Ed. 309]; Snively Groves, Inc., 109 N.L.R.B. 1394, 1395; but cf. Local 3, United Packinghouse Workers v. National Labor Relations Board (8th Cir.), 210 F.2d 325, 332-333, cert. denied, 348 U.S. 822 [75 S.Ct. 36, 99 L.Ed. 648]; Penello v. International Union, United Mine Workers (D.D.C.) 88 F.Supp. 935, 941.)
What is a “bargaining strike” in this sense depends on the purpose of 8(d). The federal act seeks to stabilize labor relations by encouraging employers and unions to negotiate and adhere to collective bargaining agreements covering the usual subjects of labor relations, such as wages, hours, and working conditions. To this end it compels employer and union to substitute to some extent collective bargaining for the economic weapons of strike and lockout as a means of creating or altering contractual relations, on the theory that collective bargaining is more likely to produce a workable contract and avoid social and economic disruption. When a collective bargaining agreement is actually in force, the statute prohibits strikes to compel changes in contractual relations at a time not contemplated by the parties, since the assurance of stable labor relations during the life of the contract is the principal incentive to entering such a contract in the first place. Thus the purpose behind section 8(d) does not encompass strikes whose aim is not to bring about a change in contractual relations, such as a strike to compel an employer to comply with his contract or to protest conduct wholly ungoverned by the contract. A union may of course bind itself not to engage in a strike for any purpose during the life of the agreement, but it is only with strikes used as a weapon in the bargaining process that Congress has in 8(d) shown sufficient concern to make them an unfair labor practice within the exclusive jurisdiction of the National [57]*57Labor Relations Board. (See Timken Roller Bearing Co. v. National Labor Relations Board (6th Cir.), 161 F.2d 949, 953-955.)
If the allegations in the complaint are true, the reason for the strike in the present case was either defendants’ contention that plaintiffs are labor contractors and are violating state safety regulations, or the personal hostility of some of the individual defendants toward plaintiffs. At no time did defendants express dissatisfaction with the terms of the contract between the parties or inform plaintiffs of a desire to modify it in any regard. The object of the strike appears to have concerned a subject wholly ungoverned by the contract and outside the usual sphere of collective bargaining. Since it was not a strike to terminate or modify the contract, it did not constitute the unfair labor practice of refusing to bargain.
Since defendants’ conduct as alleged cannot reasonably be deemed an unfair labor practice under any of the provisions of section 8(b), it is unnecessary for us to decide whether a court has jurisdiction to enjoin conduct that is in breach of a collective bargaining agreement and at the same time may be reasonably deemed an unfair labor practice. (See Independent Petroleum Workers v. Esso Standard Oil Co. (3d Cir.), 235 F.2d 401; Textile Workers Union v. Arista Mills Co. (4th Cir.), 193 F.2d 529; Dunau, Contractual Prohibition of Unfair Labor Practices: Jurisdictional Problems, 57 Colum.L. Rev. 52; but see National Labor Relations Board v. Wagner Iron Works & Bridge Workers (7th Cir.), 220 F.2d 126, 137, cert. denied, 350 U.S. 981 [76 S.Ct. 466, 467, 100 L.Ed. 850].)
Defendants contend that even if this is not a case over which the National Labor Relations Board has exclusive jurisdiction, since it is an action for breach of a collective bargaining agreement it is within the exclusive jurisdiction of the federal courts under section 301(a) of the Labor Management Relations Act. (29 U.S.C. § 185(a).) Section 301 (a) provides that: “Suits for violations of contracts between an employer and a labor organization representing employees in an industry affecting commerce . . . may be brought in any district court of the United States having jurisdiction of the parties, without respect to the amount in controversy or without regard to the citizenship of the parties.”
From the time of its enactment the federal courts were in continual disagreement as to whether section 301 required the creation of a characteristically federal decisional law to [58]*58govern collective bargaining agreements affecting interstate commerce, or merely provided a federal forum for the enforcement of substantive rights grounded in the law of the states. The majority of the lower federal courts held that section 301 created substantive rights based on federal law, and did not merely confer jurisdiction. Some were persuaded to this view by the fear that if section 301 were construed merely to extend the jurisdiction of the federal courts, it would confer upon them jurisdiction over cases not arising under the laws of the United States, and thus exceed the scope of the judicial power of the United States as defined in article III of the federal Constitution. (See Signal-Stat Corp. v. Local 475, United Elec. etc. Workers (2d Cir.), 235 F.2d 298, 300, cert. denied, 25 U.S.L. Week 3366 (U.S. June 10, 1957); Shirley-Herman Co. v. International Hod Carriers (2d Cir.), 182 F.2d 806, 808-809; International Union of Operating Engineers v. Dahlem Const. Co. (6th Cir.), 193 F.2d 470, 475; United Elec. etc. Workers v. Oliver Corp. (8th Cir.), 205 F.2d 376, 384-385.)
Recently the Court of Appeals for the First Circuit took the position that the supposed constitutional difficulty did not exist, since even if an action under 301 is based on state law, the case arises under the laws of the United States for the purposes of article III if federal court jurisdiction is necessary to implement a congressional policy governing collective bargaining agreements affecting interstate commerce. (International Brotherhood of Teamsters v. W. L. Mead, Inc., 230 F.2d 576, 580-582, cert. dismissed, 352 U.S. 802 [77 S.Ct. 21, 1 L.Ed.2d 37].) This view could have prepared the way for an interpretation of 301 that preserved the application of state law but provided a federal forum for suits against unions that because of procedural obstacles could not be sued as entities in the. courts of many states. The extremely fragmentary legislative history and almost total absence of any direction in the statute as to the content of a federal substantive law gave considerable support to such an interpretation. (Textile Workers v. American Thread Co. (D. Mass.), 113 F.Supp. 137, 139-141; see Association of Westinghouse Salaried Employees v. Westinghouse Elec. Corp., 348 U.S. 437, 441-459 [75 S.Ct. 488, 99 L.Ed. 510] (Mr. Justice Frankfurter concurring and dissenting); Wollett and Wellington, Federalism and Breach of the Labor Agreement, 7 Stan.L.Rev. 445, 472-475; Cox, Some Aspects of the Labor Management Relations Act, 1947, 61 Harv.L.Rev. 274, 303-305.)
[59]*59The United States Supreme Court, however, has now authoritatively declared that section 301 creates a federal substantive law governing collective bargaining agreements affecting interstate commerce. (Textile Workers v. Lincoln Mills of Alabama, 25 U.S.L. Week 4387 (U.S. June 3, 1957).) Although the case before the Court concerned only the power of a federal court to give a remedy not available under state law-— specific enforcement of an agreement to arbitrate—the majority opinion broadly states that “the substantive law to apply in suits under § 301(a) is federal law which the courts must fashion from the policy of our national labor laws.” “Federal interpretation of the federal law will govern, not state law. [Citation.] But state law, if compatible with the purpose of § 301, may be resorted to in order to find the rule that will best effectuate the federal policy. [Citation.] Any state law applied, however, will be absorbed as federal law and will not be an independent source of private rights.” (25 U.S.L. Week at 4389.)
It does not necessarily follow from a decision that federal law governs the rights of the parties that state courts are ousted of jurisdiction to enforce those rights. As Mr. Justice Bradley stated in Claflin v. Houseman, 93 U.S. 130, 136 [23 L.Ed. 833], “[I]f exclusive jurisdiction [in the federal courts] be neither express nor implied, the State courts have concurrent jurisdiction [to enforce federal rights] whenever, by their own constitution, they are competent to take it.” Concurrent jurisdiction exists “where it is not excluded by express provision, or by incompatibility in its exercise arising from the nature of the particular case.” (See Gerry of California v. Superior Court, 32 Cal.2d 119, 122-123 [194 P.2d 689].)
Section 301 does not expressly exclude state courts. On the contrary, it merely declares that an action for breach of a collective bargaining agreement may be brought in a federal court. Surely if Congress had intended to exclude state courts it would have used more forthright language. Nor does enforcement of collective bargaining agreements in state courts conflict with any federal policy embodied in section 301 or any other part of the federal statute. Defendants contend that the rationale of Garner v. Teamsters etc. Union, 346 U.S. 485 [74 S.Ct. 161, 98 L.Ed. 228], and Weber v. Anheuser-Busch, Inc., 348 U.S. 468 [75 S.Ct. 480, 99 L.Ed. 546], which excludes state court jurisdiction over unfair labor practices in order that the National Labor [60]*60Relations Board may be free to develop a consistent federal policy, applies equally to exclude state court jurisdiction over actions that could be brought under section 301. Section 301, however, does not confide jurisdiction to one expert tribunal for the development of federal policy, but on the contrary gives jurisdiction to all the federal district courts. The possibility of conflict between state and federal courts is no greater than the possibility of conflict among the federal courts themselves, with uniformity ultimately dependent in either case on review by the United States Supreme Court. Moreover, federal courts are no more expert than state courts in the interpretation of contracts. (See Philadelphia Marine Trade Assn. v. International Longshoremen’s Assn., 382 Pa. 326 [115 A.2d 733, 736-737], cert. denied, 350 U.S. 843 [76 S.Ct. 84, 100 L.Ed. 751]; General Elec. Co. v. International Union United Automobile etc. Workers, [Ohio Ct.App.], 108 N.E.2d 211, 219-222, appeal dismissed, 158 Ohio St. 555 [110 N.E.2d 424]; Wollett and Wellington, Federalism and Breach of the Labor Agreement, 7 Stan.L.Rev. 445, 452-455; but cf. International Plainfield Motor Co. v. Local 343, International Union United Automobile Workers, [D.N.J.], 123 F.Supp. 683, 692; note, 57 Yale L.J. 630, 637 n. 24.)
State courts therefore have concurrent jurisdiction with federal courts over actions that can be brought in the federal courts under section 301. It is obvious that in exercising this jurisdiction state courts are no longer free to apply state law, but must apply the federal law of collective bargaining agreements, otherwise the scope of the litigants’ rights will depend on the accident of the forum in which the action is brought. What the substantive federal law of collective bargaining agreements is we cannot now know. Until it is elaborated by the federal courts we assume it does not differ significantly from our own law.
If in the present case it is not necessary to determine wherein the substantive federal law differs from the law we have until now applied, another problem does press for resolution : what remedies are available in a state court vindicating rights created by section 301? It can be argued that since federal courts in actions brought under 301 cannot enjoin strikes in breach of a collective bargaining agreement because of the prohibitions of the Norris-LaGuardia Act (29 U.S.C. §§ 101, 104), state courts enforcing rights created by 301 likewise cannot issue an injunction and give a remedy not available in the federal courts.
[61]*61Some courts have broadly suggested that section 301 authorizes even federal courts to use injunctive process for the “full enforcement of the substantive rights created by section 301(a) . . . apparently notwithstanding the restrictions of the Norris-LaGuardia Act. (Milk & Ice Cream Drivers Union v. Gillespie Milk Products Corp., (6th Cir.) 203 F.2d 650, 651.) Although we do not pause to decide this question, the better view would seem to be that the inclusion of specific instances in the Labor Management Relations Act in which injunctive relief is expressly authorized negatives any general repeal of the Norris-La Guardia Act in respect to the enforcement of collective bargaining agreements. (See W. L. Mead, Inc. v. International Brotherhood of Teamsters (1st Cir.), 217 F.2d 6, 8-10, cert. dismissed, 352 U.S. 802 [77 S.Ct. 21, 1 L.Ed.2d 37]; Associated Tel. Co. v. Communication Workers, (S.D. Cal.), 114 F.Supp. 334, 340-341; United Packinghouse Workers v. Wilson & Co., (N.D. Ill.), 80 F.Supp. 563, 567-568.) By its holding in Textile Workers v. Lincoln Mills of Alabama, 25 U.S.L. Week 4387, 4389 (U.S. June 3, 1957), that the Norris-LaGuardia Act was never intended to prohibit specific enforcement of agreements to arbitrate, the Supreme Court has not suggested otherwise; strike injunctions clearly were intended to fall under the ban of the act.
If it is assumed that federal courts cannot enjoin strikes in actions under section 301 save in compliance with the strict requirements of the Norris-La Guardia Act, state courts enforcing federal rights are not necessarily subject to the same restraint. In the first place it is not entirely clear that Congress can compel a state court to withhold a remedy that would be available if the action arose under the contract law of the state. Congress can compel a state court to enforce a federal right and give a prescribed remedy when it is essential to the full realization of the right, and the state court would be competent under its own law to give a remedy of like character for a right based on state law. (Testa v. Katt, 330 U.S. 386 [67 S.Ct. 810, 91 L.Ed. 967, 172 A.L.R. 225]; Miller v. Municipal Court, 22 Cal.2d 818, 836-851 [142 P.2d 297].) Moreover, in cases brought in state courts under the Federal Employers Liability Act (45 U.S.C. § 51 et seq.), an area in which the most vexing problems of state enforcement of federal rights have arisen, it has been held that state procedure must give way if it impedes the uniform application of the federal statute essential to effectuate its purpose, even though the procedure would apply to similar actions arising [62]*62under state law. (E.g. Dice v. Akron, Canton & Youngstown R.R., 342 U.S. 359, 362-364 [72 S.Ct. 312, 96 L.Ed. 398].)
It would be a step beyond these decisions, however, to hold that a state enforcing a federal right can be compelled to withhold a remedy usually available in its courts, although it might be said that since Congress can completely exclude state jurisdiction it can dictate that certain remedies be withheld if necessary to implement federal policy. Some light is thrown on this question by Brown v. Gerdes, 321 U.S. 178 [64 S.Ct. 487, 88 L.Ed. 659], In that case the court held that the Federal Bankruptcy Act deprived a state court of power to fix or grant fees to counsel for trustees, even though they had performed services in actions before the court and under state law were entitled to a lien on their client’s cause of action. (See also Hines v. Lowrey, 305 U.S. 85 [59 S.Ct. 31, 83 L.Ed. 56].) This decision, however, does not settle the precise issue before us, and a strong argument can be made that Congress must take the state courts as it finds them in regard to the availability of equitable remedies, and can require only that they not discriminate against litigants enforcing federal rights.
In the converse situation, when a federal court enforces a state-created right and jurisdiction is based on diversity of citizenship, it was established that the court could give an equitable remedy not available under state law (Guffey v. Smith, 237 U.S. 101 [35 S.Ct. 526, 59 L.Ed. 856]; see Guaranty Trust Co. v. York, 326 U.S. 99, 105-106 [65 S.Ct. 1464, 89 L.Ed. 2079, 160 A.L.R. 1231]), or withhold a remedy that was available under state law. (Pusey & Jones Co. v. Hanssen, 261 U.S. 491, 494-499 [43 S.Ct. 454, 67 L.Ed. 763].) Considerable doubt has been cast on the vitality of this doctrine by decisions stressing more and more that the goal of diversity jurisdiction is substantial similarity of outcome whether an action is brought in a state or federal court, and that remedies often go to the substance of the right. (E.g. Bernhardt v. Polygraphic Co., 350 U.S. 198, 202-204 [76 S.Ct. 273, 100 L.Ed. 199]; cf. Angel v. Bullington, 330 U.S. 183, 191-192 [67 S.Ct. 657, 91 L.Ed. 832].) Whatever the implications of diversity jurisdiction, however, they do not necessarily determine whether a state court, under the compulsion of the supremacy clause, must withhold a specific remedy. A state court enforcing a federal right is not simply another federal court. (Minneapolis & St. Louis R.R. v. Bombolis, 241 U.S. 211, 222 [36 S.Ct. 595, 60 L.Ed. 961].)
[63]*63The difficulties that inhere in the question of congressional power to control equitable remedies available in state courts strengthen our conviction that, whether or not Congress could deprive state courts of the power to give such remedies when enforcing collective bargaining agreements, it has not attempted to do so either in the Norris-La Guardia Act or section 301.
The Norris-La Guardia Act is in terms drawn as a limitation on the courts of the United States. “No court of the United States,” declares section 1, “shall have jurisdiction to issue any . . . injunction in a case involving or growing out of a labor dispute . . . and a court of the United States is defined in section 13(d) as “any court of the United States whose jurisdiction has been or may be conferred or defined or limited by Acts of Congress, including the courts of the District of Columbia.” (29 U.S.C. §§101, 113(d).) The statute aimed to restrict the federal equity power, and was justified constitutionally on the basis of Congress’ power to regulate the jurisdiction of the federal courts. (Brotherhood of B.B. Trainmen v. Toledo, Peoria & Western R.R., 321 U.S. 50, 58, 63 [64 S.Ct. 413, 88 L.Ed. 534, 150 A.L.R. 810]; Lauf v. E. G. Shinner & Co., 303 U.S. 323, 330 [58 S.Ct. 578, 82 L.Ed. 872].) It did not limit the remedial power of the state courts (see United Elec. etc. Workers v. Westinghouse Elec. Corp., (E.D. Pa.), 65 F.Supp. 420, 422; General Bldg. Contractors’ Assn. v. Local Unions, 370 Pa. 73 [87 A.2d 250, 254]; Markham & Callow, Inc. v. International Woodworkers etc. Union, 170 Ore. 517 [135 P.2d 727, 746], citing Frankfurter and Greene, The Labor Injunction at 220; 39 Ops. U.S. Atty. Gen. 242, 246), and could not constitutionally have done so since its prohibition was not restricted to injunctions in labor disputes affecting interstate commerce or any other subject over which Congress has paramount power.
Section 301 of the Labor Management Relations Act does not embody any policy that requires a state court enforcing rights created by that section to withhold injunctive relief. The principal purpose of section 301 was to facilitate the enforcement of collective bargaining agreements by making unions suable as entities in the federal courts, and thereby to remedy the one-sided character of existing labor legislation. (See United Packinghouse Workers v. Wilson & Co., (N.D. Ill.), 80 F.Supp. 563, 568.) We would give altogether too ironic a twist to this purpose if we held that the actual [64]*64effect of the legislation was to abolish in state courts equitable remedies that had been available, and leave an employer in a worse position in respect to the effective enforcement of his contract than he was before the enactment of section 301.
Nothing in the nature of the rights created by section 301 requires that injunctive relief be denied in their enforcement. Such relief would of course not impair any federal contract right, nor would it expand it in conflict with any policy that we have been able to discern in the statute. To the contrary, the principal purpose of the statute is to encourage the formation and effective enforcement of collective bargaining agreements. (See Textile Workers v. Lincoln Mills of Alabama, 25 U.S.L. Week 4387, 4388 and n. 4 (U.S. June 3, 1957).) The restriction on the remedies available in the federal courts arises not from any policy in the Labor Management Relations Act itself but from the Norris-La Guardia Act, and the policy of that statute as we have seen is confined to the federal courts. (See Associated Tel. Co. v. Communication Workers, (S.D. Cal.), 114 F.Supp. 334, 341; Philadelphia Marine Trade Assn. v. International Longshoremen’s Assn., 382 Pa. 326 [115 A.2d 733, 736], cert. denied, 350 U.S. 843 [76 S.Ct. 84, 100 L.Ed. 751]; Wollett and Wellington, Federalism and Breach of the Labor Agreement, 7 Stan.L.Rev. 445, 456-460.)
Finally, there is no invariable requirement, implicit in the federal system, that a state court enforcing a federal right must not go beyond the remedies available in a federal court. Uniformity in the determination of the substantive federal right itself is no doubt a necessity, but such uniformity is not threatened because a state court can give a more complete and effective remedy. Several federal courts, proceeding on the hypothesis that substantive rights in actions under section 301 arise out of state law, have concluded that the federal court is not confined to the remedies available in the state courts. (Local 205, United Elec. Workers v. General Elec. Co., 233 F.2d 85, 94-95, aff’d on other grounds, 25 U.S.L. Week 4391 (U.S. June 3, 1957); Textile Workers v. American Thread Co., (D. Mass), 113 F.Supp. 137, 141; See Cox, Grievance Arbitration in the Federal Courts, 67 Harv.L.Rev. 591, 601.) We cannot see why, under the opposite hypothesis, it is not equally true that a state court is not confined to remedies available in a federal court when the restriction on the federal court does not flow from the statute creating the federal right.
[65]*65As a final attack on the jurisdiction of the trial court, defendants contend that plaintiffs are precluded from maintaining the present action because the issue involved is referable to arbitration under the collective bargaining agreement. The issue defendants contend must be arbitrated is whether the strike was in breach of the contract.
Article III (A) of the contract provides that, “it is the purpose and intent of the parties hereto that all grievances or disputes arising between them over the interpretation or application of the terms of this Agreement shall be settled by the procedure set forth in Article V hereof, and that during the term of this Agreement the Unions . . . shall not . . . call or engage in, sanction, or assist in a strike against . . . the Contractors. . . .” Article V is entitled, “Procedure For Settlement of Grievances and Disputes.” In paragraph A it provides that employees are to present grievances and disputes to their craft steward, who will report them to a special representative. The special representative will then attempt to adjust the dispute with the contractor. Paragraphs C and D provide that if this method of settlement fails, the dispute or grievance may be referred to a Joint Conference Board and from there to a Joint Arbitration Committee. If a majority vote of the Joint Arbitration Committee cannot be obtained, the grievance or dispute is to be submitted to an arbiter whose award is final and binding. Paragraph B repeats the provision of article III that all disputes or grievances arising out of the interpretation or application of any of the terms or conditions of the contract shall be determined by the procedure set forth in article V.
The arbitrability of a dispute may itself be subject to arbitration if the parties have so provided in their contract. In this situation the court should stay proceedings pending the arbiter’s determination of his own jurisdiction unless it is clear that the claim of arbitrability is wholly groundless. (See International Union, United Automobile Workers v. Benton Harbor Malleable Industries (6th Cir.), 242 F.2d 536, 539, petition for cert. filed, 25 U.S.L. Week 3361 (U.S. May 24, 1957); Local 205, United Elec. etc. Workers v. General Elec. Co. (1st Cir.), 233 F.2d 85, 101, aff’d, 25 U.S.L. Week 4391 (U.S. June 3, 1957); Scoles, Review of Labor Arbitration Awards on Jurisdictional Grounds, 17 U.Chi.L. Rev. 616, 620-621.) Of course, even when the parties have conferred upon the arbiter the unusual power of de[66]*66termining bis own jurisdiction, tbe court cannot avoid the necessity of making a certain threshhold determination of arbitrability, namely, whether the parties have in fact conferred this power on the arbiter. There is no indication in the present contract that the parties intended any such result. It may be that leaving to an arbiter the question of arbitrability is a desirable procedure from the point of view of harmonious labor relations (see Arbitrability, 1951 Report of the Committee on Improvement of Administration of Union-Employer Contracts, Section of Labor Relations Law, American Bar Assn., in Readings on Labor Law 172, 192-194 (Reynard ed. 1955)), although some have expressed fear that the procedure may be used to bring about unbargained for changes in the relations of the parties. (See minority report in id. at 201.) Whatever the merits of the procedure, we think it sufficiently outside the usual understanding of the relations of court and arbiter and their respective functions to assume that the parties expected a court determination of arbitrability unless they have clearly stated otherwise. (See Philadelphia Marine Trade Assn. v. International Longshoremen’s Assn., 382 Pa. 326 [115 A.2d 733, 738], cert. denied, 350 U. S. 843 [76 S.Ct. 84, 100 L.Ed. 751].)
Plaintiffs take the position that defendants’ breach of contract is not an issue referable to arbitration because by striking in violation’ of the no-strike clause defendants have themselves repudiated the arbitration procedure. This argument misconceives the question since it assumes that defendants have in fact breached the no-strike provision, the very issue that defendants dispute and say must go to arbitration. All strikes during the life of a contract are not necessarily violations of a no-strike clause, even though on its face the prohibition appears to be absolute. (See The No-Strike Clause, 1952 Report of the Committee on Improvement of Administration of Union-Employer Contracts, Section of Labor Relations Law, American Bar Assn., in Readings on Labor Law 255, 275-277 [Reynard ed. 1955).) The question is whether the collective bargaining agreement requires arbitration to determine if defendants’ conduct violates the no-strike clause, or whether the court itself may make this determination. As with all problems of contract interpretation, the answer must reflect the intention of the parties.
This same question has been before the lower federal courts on numerous occasions. Many of the decisions, although helpful, are not determinative of the problem before us be[67]*67cause they turn on the language of a particular collective bargaining agreement. Some of the decisions are in irreconcilable conflict.1
We think the trial court was right in concluding that the parties to the contract in the present case did not contemplate arbitration of a breach of the no-strike clause. It is true that the language of the arbitration provision is broad, stating that “all grievances or disputes arising between . . . [the parties] over the interpretation or application of the terms of this Agreement shall be settled by the procedure set forth in Article Y. . . .” If this were the only provision to be considered, it might reasonably be argued that the question of whether a strike is in breach of contract is arbitrable since it involves interpretation of a term of the contract. The contract, however, must be read as a whole and the grievance and arbitration procedure viewed in the light of its purpose.
The grievance procedure set forth in article V is designed primarily to cope with the usual employee complaints concerning working conditions, wrongful discharge, and the like. The first steps in the procedure require a grievance to be submitted to a craft steward and then reported to a special representative for adjustment. It is inconceivable that the [68]*68parties thought an employer would be required to follow these steps in prosecuting his objection to a strike. It is possible that they expected employer complaints to be presented directly to the Joint Conference Board or the Joint Arbitration Committee. The later steps in the grievance procedure, however, and arbitration itself, appear to be integrated parts of a single scheme for the settlement of disputes. They are to be resorted to when the earlier steps in the procedure have failed to yield a settlement, and purport to dispose of the same disputes and grievances that are the subject of the earlier steps.
A more persuasive consideration, however, is the relation between the grievance and arbitration procedure and the no-strike guarantee. The grievance and arbitration procedure is an alternative to the strike as a means of settling disputes, and it is clear that the parties bound themselves to resort to this procedure for the very purpose of avoiding the possibility of a strike. The parties’ intention is shown by the fact that defendants’ promise in article III not to resort to a strike follows immediately after their promise to use the grievance procedure. Moreover, the preamble to the contract states that, “it is the desire of the parties hereto to provide, establish and put into practice effective methods for the settlement of misunderstandings, disputes or grievances between the parties hereto to the end that the Contractors are assured continuity of operation and the members of the Unions are assured continuity of employment, and industrial peace is maintained. ...” The grievance and arbitration procedure assumes that work goes on. Resort to the procedure is designed to avoid the necessity of a strike, not to adjudicate a strike once it has occurred, and the purpose of the procedure limits its applicability. (See International Union, United Automobile Workers v. Benton Harbor Malleable Industries (6th Cir.), 242 F.2d 536, 540-541, petition for cert. filed, 25 U.S.L. Week 3361 (U.S. May 24, 1957).)
It is urged that arbitration provisions in collective bargaining agreements should when possible be construed broadly to cover all disputes between the parties to the end that the contract will provide a complete system of government for the parties, a system far more satisfactory than any the courts can provide and, because established by the parties themselves, more likely to lead to industrial peace. We do not dispute the attractiveness of the ideal, but it does not justify overriding the parties’ intentions and forcing on them a method of decision wholly unexpected in its appli[69]*69cation. As Mr. Justice Cardozo pointed out in Marchant v. Mead-Morrison Mfg. Co., 252 N.Y. 284 [169 N.E. 386, 391, 393], “Courts are not at liberty to shirk the process of construction under the empire of a belief that arbitration is beneficent, any more than they may shirk it if their belief happens to be the contrary. No one is under a duty to resort to these conventional tribunals, however helpful their processes, except to the extent he has signified his willingness. . . . [The contracting parties] . . . are not to be trapped by a strained and unnatural construction of words of doubtful import into an abandonment of legal remedies, unwilled and unforeseen. ’ ’
There is no merit in defendants’ contention that because plaintiffs did not have the contractor’s license required by sections 7025-7031 of the Business and Professions Code, they are barred from maintaining the present action by section 7031 or the common-law rule that illegal contracts will not be enforced. Section 7031 bars actions “for the collection of compensation” for contracting work, not actions to enforce collective bargaining agreements. Plaintiffs do not seek to enforce an illegal contract; their labor contract is not prohibited by the licensing statute and its validity is unrelated to the question whether plaintiffs can legally enter into construction contracts. If plaintiffs failed to obtain a partnership license, they are not for that reason completely outside the protection of the law and denied relief from torts committed against them or breaches of contract other than contracts to recover compensation. (See Grant v. Weatherholt, 123 Cal.App.2d 34, 42-44 [266 P.2d 185].)
Finally, there was sufficient evidence to justify the issuance of the preliminary injunction. Defendants do not deny the strike, nor on this appeal do they contend, as they did in the trial court, that the contract was not in force at the time of the strike or that plaintiffs were not parties to it. The reasons for the strike are obscure. There is some indication that defendants objected to plaintiffs on the grounds that they were labor contractors and violating state safety regulations. Defendants failed, however, to explain precisely what labor contracting is, to show that plaintiffs were engaged in it, or even if they were, that defendants were justified in striking rather than resorting to the grievance procedure. The evidence tended to show that plaintiffs had not violated any state safety regulation. There was substantial evidence to support plaintiffs’ claim that the strike was in breach of [70]*70contract and that they would be irreparably injured if it continued.
The order is affirmed.
Gibson, C. J., Spence, J., and McComb, J., concurred.
Shenk, J., and Schauer, J., concurred in the judgment.