Mr. Justice Frankfurter
delivered the opinion of the Court.
Petitioner, a national of the United States by birth, has been declared to have lost his American citizenship by operation of the Nationality Act of 1940, 54 Stat. 1137, as amended by the Act of September 27, 1944, 58 Stat. 746. Section 401 of that Act1 provided that
“A person who is a national of the United States, whether by birth or naturalization, shall lose his nationality by:
“(e) Voting in a political election in a foreign state or participating in an election or plebiscite to determine the sovereignty over foreign territory; or
[46]*46“(j) Departing from or remaining outside of the jurisdiction of the United States in time of war or during a period declared by the President to be a period of national emergency for the purpose of evading or avoiding training and service in the land or naval forces of the United States.”
He seeks a reversal of the judgment against him on the ground that these provisions were beyond the power of Congress to enact.
Petitioner was born in Texas in 1909. He resided in the United States until 1919 or 1920, when he moved with his parents to Mexico, where he lived, apparently without interruption, until 1943. In 1928 he was informed that he had been born in Texas. At the outbreak of World War II, petitioner knew of the duty of male United States citizens to register for the draft, but he failed to do so. In 1943 he applied for admission to the United States as an alien railroad laborer, stating that he was a native-born citizen of Mexico, and was granted permission to enter on a temporary basis. He returned to Mexico in 1944 and shortly thereafter applied for and was granted permission, again as a native-born Mexican citizen, to enter the United States temporarily to continue his employment as a railroad laborer. Later in 1944 he returned to Mexico once more. In 1947 petitioner applied for admission to the United States at El Paso, Texas, as a citizen of the United States. At a Board of Special Inquiry hearing (and in his subsequent appeals to the Assistant Commissioner and the Board of Immigration Appeals), he admitted having remained outside of the United States to avoid military service and having voted in political elections in Mexico. He was ordered excluded on the ground that he had expatriated himself; this order was affirmed on appeal. In 1952 petitioner, claiming to be a native-born citizen of Mexico, [47]*47was permitted to enter the United States as an alien agricultural laborer. He surrendered in 1953 to immigration authorities in San Francisco as an alien unlawfully in the United States but claimed the right to remain by virtue of his American citizenship. After a hearing before a Special Inquiry Officer, he was ordered deported as an alien not in possession of a valid immigration visa; this order was affirmed on appeal to the Board of Immigration Appeals.
Petitioner brought suit in 1954 in a United States District Court for a judgment declaring him to be a national of the United States.2 The court, sitting without a jury, found (in addition to the undisputed facts set forth above) that petitioner had remained outside of the United States from November 1944 to July 1947 for the purpose of avoiding service in the armed forces of the United States and that he had voted in a “political election” in Mexico in 1946. The court, concluding that he had thereby expatriated himself, denied the relief sought by the petitioner. The United States Court of Appeals for the Ninth Circuit affirmed. 235 F. 2d 364. We granted certiorari because of the constitutional questions raised by the petitioner. 352 U. S. 908.
[48]*48Statutory expatriation, as a response to problems of international relations, was first introduced just a half century ago. Long before that, however, serious friction between the United States and other nations had stirred consideration of modes of dealing with the difficulties that arose out of the conflicting claims to the allegiance of foreign-born persons naturalized in the United States, particularly when they returned to the country of their origin.
As a starting point for grappling with this tangle of problems, Congress in 1868 formally announced the traditional policy of this country that it is the “natural and inherent right of all people” to divest themselves of their allegiance to any state, 15 Stat. 223, R. S. § 1999. Although the impulse for this legislation had been the refusal by other nations, notably Great Britain, to recognize a right in naturalized Americans who had been their subjects to shed that former allegiance, the Act of 1868 was held by the Attorney General to apply to divestment by native-born and naturalized Americans of their United States citizenship. 14 Op. Atty. Gen. 295, 296. In addition, while the debate on the Act of 1868 was proceeding, negotiations were completed on the first of a series of treaties for the adjustment of some of the disagreements that were constantly arising between the United States and other nations concerning citizenship. These instruments typically provided that each of the signatory nations would regard as a citizen of the other such of its own citizens as became naturalized by the other. E. g., Treaty with the North German Confederation, Feb. 22, 1868, 2 Treaties, Conventions, International Acts, etc. (comp. Malloy, 1910), 1298. This series of treaties initiated this country's policy of automatic divestment of citizenship for specified conduct affecting our foreign relations.
[49]*49On the basis, presumably, of the Act of 1868 and such treaties as were in force, it was the practice of the Department of State during the last third of the nineteenth century to make rulings as to forfeiture of United States citizenship by individuals who performed various acts abroad. See Borchard, Diplomatic Protection of Citizens Abroad, §§ 319, 324. Naturalized citizens who returned to the country of their origin were held to have abandoned their citizenship by such actions as accepting public office there or assuming political duties. See Davis to Weile, Apr. 18, 1870, 3 Moore, Digest of International Law, 737; Davis to Taft, Jan. 18, 1883, 3 id., at 739. Native-born citizens of the United States (as well as naturalized citizens outside of the country of their origin) were generally deemed to have lost their American citizenship only if they acquired foreign citizenship. See Bayard to Suzzara-Verdi, Jan. 27, 1887, 3 id., at 714; see also Comitis v. Parkerson, 56 F. 556, 559.
No one seems to have questioned the necessity of having the State Department, in its conduct of the foreign relations of the Nation, pass on the validity of claims to American citizenship and to such of its incidents as the right to diplomatic protection. However, it was recognized in the Executive Branch that the Department had no specific legislative authority for nullifying citizenship, and several of the Presidents urged Congress to define the acts by which citizens should be held to have expatriated themselves. E. g., Message of President Grant to Congress, Dec. 7, 1874, 7 Messages and Papers of the Presidents (Richardson ed. 1899) 284, 291-292. Finally in 1906, during the consideration of the bill that became the Naturalization Act of 1906, a Senate resolution and a recommendation of the House Committee on Foreign Affairs called for an examination of the problems relating to American citizenship, expatriation and protection [50]*50abroad. In response to these suggestions the Secretary of State appointed the Citizenship Board of 1906, composed of the Solicitor of the State Department, the Minister to the Netherlands and the Chief of the Passport Bureau. The board conducted a study and late in 1906 made an extensive report with recommendations for legislation.
Among the recommendations of the board were that expatriation of a citizen “be assumed” when, in time of peace, he became naturalized in a foreign state, engaged in the service of a foreign state where such service involved the taking of an oath of allegiance to that state, or domiciled in a foreign state for five years with no intention to return. Citizenship of the United States, Expatriation, and Protection Abroad, H. R. Doc. No. 326, 59th Cong., 2d Sess. 23. It also recommended that an American woman who married a foreigner be regarded as losing her American citizenship during coverture. Id., at 29. As to the first two recommended acts of expatriation, the report stated that “no man should be permitted deliberately to place himself in a position where his services may be claimed by more than one government and his allegiance be due to more than one.” Id., at 23. As to the third, the board stated that more and more Americans were going abroad to live “and the question of their protection causes increasing embarrassment to this Government in its relations with foreign powers.” Id., at 25.
Within a month of the submission of this report a bill was introduced in the House by Representative Perkins of New York based on the board’s recommendations. Perkins’ bill provided that a citizen would be “deemed to have expatriated himself” when, in peacetime, he became naturalized in a foreign country or took an oath of allegiance to a'foreign state; it was presumed that a naturalized citizen who resided for five years in a foreign state had [51]*51ceased to be an American citizen, and an American woman who married a foreigner would take the nationality of her husband. 41 Cong. Rec. 1463-1464. Perkins stated that the bill was designed to discourage people from evading responsibilities both to other countries and to the United States and “to save our Government [from] becoming-involved in any trouble or question with foreign countries where there is no just reason.” Id., at 1464. What little debate there was on the bill centered around the foreign domicile provision; no constitutional issue was canvassed. The bill passed the House, and, after substantially no debate and the adoption of a committee amendment adding a presumption of termination of citizenship for a naturalized citizen who resided for two years in the country of his origin, 41 Cong. Rec. 4116, the Senate passed it and it became the Expatriation Act of 1907. 34 Stat. 1228.
The question of the power of Congress to enact legislation depriving individuals of their American citizenship was first raised in the courts by Mackenzie v. Hare, 239 U. S. 299. The plaintiff in that action, Mrs. Mackenzie, was a native-born citizen and resident of the United States. In 1909 she married a subject of Great Britain and continued to reside with him in the United States. When, in 1913, she applied to the defendants, members of a board of elections in California, to be registered as a voter, her application was refused on the ground that by reason of her marriage she had ceased to be a citizen of the United States. Her petition for a writ of mandamus was denied in the state courts of California, and she sued out a writ of error here, claiming that if the Act of 1907 was intended to apply to her it was beyond the power of Congress. The Court, through Mr. Justice McKenna, after finding that merging the identity of husband and wife, as Congress had done in this instance, had [52]*52a “purpose and, it may be, necessity, in international policy,” continued:
“As a government, the United States is invested with all the attributes of sovereignty. As it has the character of nationality it has the powers of nationality, especially those which concern its relations and intercourse with other countries. We should hesitate long before limiting or embarrassing such powers. ... We concur with counsel that citizenship is of tangible worth, and we sympathize with plaintiff in her desire to retain it and in her earnest assertion of it. But there is involved more than personal considerations. As we have seen, the legislation was urged by conditions of national moment.... It is the conception of the legislation under review that such an act may bring the Government into embarrassments and, it may be, into controversies. . . .” 239 U. S., at 311-312.
The Court observed that voluntary marriage of an American woman with a foreigner may have the same consequences, and “involve national complications of like kind,” as voluntary expatriation in the traditional sense. It concluded: “This is no arbitrary exercise of government.” 239 U. S., at 312. See also Ex parte Griffin, 237 F. 445; Ex parte Ng Fung Sing, 6 F. 2d 670.
By the early 1930’s, the American law on nationality, including naturalization and denationalization, was expressed in a large number of provisions scattered throughout the statute books. Some of the specific laws enacted at different times seemed inconsistent with others, some problems of growing importance had emerged that Congress had left unheeded. At the request of the House Committee on Immigration and Naturalization, see 86 Cong. Rec. 11943, President Franklin D. Roosevelt established a Committee composed of the Secretary of State, [53]*53the Attorney General and the Secretary of Labor to review the nationality laws of the United States, to recommend revisions and to codify the nationality laws into one comprehensive statute for submission to Congress; he expressed particular concern about “existing discrimina-tions” in the law. Exec. Order No. 6115, Apr. 25, 1933. The necessary research for such a study was entrusted to specialists representing the three departments. Five years were spent by these officials in the study and formulation of a draft code. In their letter submitting the draft code to the President after it had been reviewed within the Executive Branch, the Cabinet Committee noted the special importance of the provisions concerning loss of nationality and asserted that none of these provisions was “designed to be punitive or to interfere with freedom of action”; they were intended to deprive of citizenship those persons who had shown that “their real attachment is to the foreign country and not to the United States.” Codification of the Nationality Laws of the United States, H. R. Comm. Print, Pt. 1, 76th Cong., 1st Sess. v-vn.
The draft code of the Executive Branch was an omnibus bill in five chapters. The chapter relating to “Loss of Nationality” provided that any citizen should “lose his nationality” by becoming naturalized in a foreign country; taking an oath of allegiance to a foreign state; entering or serving in the armed forces of a foreign state; being employed by a foreign government in a post for which only nationals of that country are eligible; voting in a foreign political election or plebiscite; using a passport of a foreign state as a national thereof; formally renouncing American citizenship before a consular officer abroad; deserting the armed forces of the United States in wartime (upon conviction by court martial); if a naturalized citizen, residing in the state of his former nationality or birth for two years if he thereby acquires the nationality of that state; or, if a naturalized citizen, [54]*54residing in the state of his former nationality or birth for three years. Id., at 66-76.
In support of the recommendation of voting in a foreign political election as an act of expatriation, the Committee reported:
“Taking an active part in the political affairs of a foreign state by voting in a political election therein is believed to involve a political attachment and practical allegiance thereto which is inconsistent with continued allegiance to the United States, whether or not the person in question has or acquires the nationality of the foreign state. In any event it is not believed that an American national should be permitted to participate in the political affairs of a foreign state and at the same time retain his American nationality. The two facts would seem to be inconsistent with each other.” Id., at 67.
As to the reference to plebiscites in the draft language, the report states: “If this provision had been in effect when the Saar Plebiscite was held, Americans voting in it would have been expatriated.” Ibid. It seems clear that the most immediate impulse for the entire voting provision was the participation by many naturalized Americans in the plebiscite to determine sovereignty over the Saar in January 1935. H. R. Rep. No. 216, 74th Cong., 1st Sess. 1. Representative Dickstein of New York, Chairman of the House Committee on Immigration and Naturalization, who had called the plebiscite an “international dispute” in which naturalized American citizens could not properly participate, N. Y. Times, Jan. 4, 1935, p. 12, col. 3, had introduced a bill in the House in 1935 similar in language to the voting provisions in the draft code, 79 Cong. Rec. 2050, but, although it was favorably reported, the House did not pass it.
[55]*55In June 1938 the President submitted the Cabinet Committee’s draft code and the supporting report to Congress. In due course, Chairman Dickstein introduced the code as H. R. 6127, and it was referred to his committee. In early 1940 extensive hearings were held before both a subcommittee and the full committee at which the interested Executive Branch agencies and others testified. With respect to the voting provision, Chairman Dickstein spoke of the Americans who had voted in the Saar plebiscite and said, “If they are American citizens they had no right to vote, to interfere with foreign matters or political subdivision.” Hearings before the House Committee on Immigration and Naturalization on H. R. 6127, 76th Cong., 1st Sess. 287. Mr. Flournoy, Assistant Legal Adviser of the State Department, said that the provision would be “particularly applicable” to persons of dual nationality, id., at 132; however, a suggestion that the provision be made applicable only to dual nationals, id., at 398, was not adopted.
Upon the conclusion of the hearings in June 1940 a new bill was drawn up and introduced as H. R. 9980. The only changes from the Executive Branch draft with respect to the acts of expatriation were the deletion of using a foreign passport and the addition of residence by a naturalized citizen for five years in any foreign country as acts that would result in loss of nationality. 86 Cong. Rec. 11960-11961. The House debated the bill for a day in September 1940. In briefly summarizing the loss of nationality provisions of the bill, Chairman Dickstein said that “this bill would put an end to dual citizenship and relieve this country of the responsibility of those who reside in foreign lands and only claim citizenship when it serves their purpose.” Id., at 11944. Representative Rees of Kansas, who had served as chairman of the subcommittee that studied the draft code, said that clarifying [56]*56legislation was needed, among other reasons, “because of the duty of the Government to protect citizens abroad.” Id., at 11947. The bill passed the House that same day. Id., at 11965.
In the Senate also, after a favorable report from the Committee on Immigration, the bill was debated very briefly. Committee amendments were adopted making the provision on foreign military service applicable only to dual nationals, making treason an act of expatriation and providing a procedure by which persons administratively declared to have expatriated themselves might obtain judicial determinations of citizenship. The bill as amended was passed. Id., at 12817-12818. The House agreed to these and all other amendments on which the Senate insisted, id., at 13250, and, on October 14, the Nationality Act of 1940 became law. 54 Stat. 1137.
The loss of nationality provisions of the Act constituted but a small portion of a long omnibus nationality statute. It is not surprising, then, that they received as little attention as they did in debate and hearings and that nothing specific was said about the constitutional basis for their enactment. The bill as a whole was regarded primarily as a codification — and only secondarily as a revision — of statutes that had been in force for many years, some of them, such as the naturalization provisions, having their beginnings in legislation 150 years old. It is clear that, as is so often the case in matters affecting the conduct of foreign relations, Congress was guided by and relied very heavily upon the advice of the Executive Branch, and particularly the State Department. See, e. g., 86 Cong. Rec. 11943-11944. In effect, Congress treated the Cabinet Committee as it normally does its own committees charged with studying a problem and formulating legislation. These considerations emphasize the importance, in the inquiry into congressional power in this field, of keeping in mind the historical background [57]*57of the challenged legislation, for history will disclose the purpose fairly attributable to Congress in enacting the statute.
The first step in our inquiry must be to answer the question: what is the source of power on which Congress must be assumed to have drawn? Although there is in the Constitution no specific grant to Congress of power to enact legislation for the effective regulation of foreign affairs, there can be no doubt of the existence of this power in the law-making organ of the Nation. See United States v. Curtiss-Wright Export Corp., 299 U. S. 304, 318; Mackenzie v. Hare, 239 U. S. 299, 311-312. The States that joined together to form a single Nation and to create, through the Constitution, a Federal Government to conduct the affairs of that Nation must be held to have granted that Government the powers indispensable to its functioning effectively in the company of sovereign nations. The Government must be able not only to deal affirmatively with foreign nations, as it does through the maintenance of diplomatic relations with them and the protection of American citizens sojourning within their territories. It must also be able to reduce to a minimum the frictions that are unavoidable in a world of sovereigns sensitive in matters touching their dignity and interests.
The inference is fairly to be drawn from the congressional history of the Nationality Apt of 1940, read in light of the historical background of expatriation in this country, that, in making voting in foreign elections (among other behavior) an act of expatriation, Congress was seeking to effectuate its power to regulate foreign affairs. The legislators, counseled by those on whom they rightly relied for advice, were concerned about actions by citizens in foreign countries that create problems of protection and are inconsistent with American allegiance. Moreover, we cannot ignore the fact that embarrassments [58]*58in the conduct of foreign relations were of primary concern in the consideration of the Act of 1907, of which the loss of nationality provisions of the 1940 Act are a codification and expansion.
Broad as the power in the National Government to regulate foreign affairs must necessarily be, it is not without limitation. The restrictions confining Congress in the exercise of any of the powers expressly delegated to it in the Constitution apply with equal vigor when that body seeks to regulate our relations with other nations. Since Congress may not act arbitrarily, a rational nexus must exist between the content of a specific power in Congress and the action of Congress in carrying that power into execution. More simply stated, the means — in this case, withdrawal of citizenship — must be reasonably related to the end — here, regulation of foreign affairs. The inquiry — -and, in the case before us, the sole inquiry — into which this Court must enter is whether or not Congress may have concluded not unreasonably that there is a relevant connection between this fundamental source of power and the ultimate legislative action.3
[59]*59Our starting point is to ascertain whether the power of Congress to deal with foreign relations may reasonably be deemed to include a power to deal generally with the active participation, by way of voting, of American citizens in foreign political elections. Experience amply attests that, in this day of extensive international travel, rapid communication and widespread use of propaganda, the activities of the citizens of one nation when in another country can easily cause serious embarrassments to the government of their own country as well as to their fellow citizens. We cannot deny to Congress the reasonable belief that these difficulties might well become acute, to the point of jeopardizing the successful conduct of international relations, when a citizen of one country chooses to participate in the political or governmental affairs of another country. The citizen may by his action unwittingly promote or encourage a course of conduct contrary to the interests of his own government; moreover, the people or government of the foreign country may regard his action to be the action of his government, or at least as a reflection if not an expression of its policy. Cf. Preuss, International Responsibility for Hostile Propaganda Against Foreign States, 28 Am. J. Int’l L. 649, 650.
It follows that such activity is regulable by Congress under its power to deal with foreign affairs. And it must be regulable on more than an ad hoc basis. The subtle influences and repercussions with which the Government must deal make it reasonable for the generalized, although clearly limited, category of “political election” to be used in defining the area of regulation. That description carries with it the scope and meaning of its context and purpose; classes of elections — nonpolitical in the col[60]*60loquial sense — as to which participation by Americans could not possibly have any effect on the relations of the United States with another country are excluded by any rational construction of the phrase. The classification that Congress has adopted cannot be said to be inappropriate to the difficulties to be dealt with. Specific applications are of course open to judicial challenge, as are other general categories in the law, by a “gradual process of judicial inclusion and exclusion.” Davidson v. New Orleans, 96 U. S. 97, 104.4
The question must finally be faced whether, given the power to attach some sort of consequence to voting in a foreign political election, Congress, acting under the Necessary and Proper Clause, Art. I, § 8, cl. 18, could attach loss of nationality to it. Is the means, withdrawal of citizenship, reasonably calculated to effect the end that is within the power of Congress to achieve, the avoidance of embarrassment in the conduct of our foreign relations attributable to voting by American citizens in foreign political elections? The importance and extreme delicacy of the matters here sought to be regulated demand that Congress be permitted ample scope in selecting appropriate modes for accomplishing its purpose. The critical connection between this conduct and loss of citizenship is the fact that it is the possession of American citizenship by a person committing the act that makes the act potentially embarrassing to the American Government and pregnant with the possibility of embroiling this country in disputes with other nations. The termination of citizenship terminates the problem. Moreover, the fact is not without significance that Congress has interpreted [61]*61this conduct, not irrationally, as importing not only something less than complete and unswerving allegiance to the United States but also elements of an allegiance to another country in some measure, at least, inconsistent with American citizenship.
Of course, Congress can attach loss of citizenship only as a consequence of conduct engaged in voluntarily. See Mackenzie v. Hare, 239 U. S. 299, 311-312. But it would be a mockery of this Court’s decisions to suggest that a person, in order to lose his citizenship, must intend or desire to do so. The Court only a few years ago said of the person held to have lost her citizenship in Mackenzie v. Hare, supra: “The woman had not intended to give up her American citizenship.” Savorgnan v. United States, 338 U. S. 491, 501. And the latter case sustained the denationalization of Mrs. Savorgnan although it was not disputed that she “had no intention of endangering her American citizenship or of renouncing her allegiance to the United States.” 338 U. S., at 495.5 What both women did do voluntarily was to engage in conduct to which Acts of Congress attached the consequence of denationalization irrespective of — and, in those cases, absolutely contrary to — the intentions and desires of the individuals. Those two cases mean nothing — indeed, they are deceptive — if their essential significance is not rejection of the notion that the power of Congress to terminate citizenship depends upon the citizen’s assent. It is a distortion of those cases to explain them away on a theory that a citizen’s assent to denationalization may be inferred from his having engaged in conduct that amounts to an “abandonment of citizenship” or a “trans[62]*62fer of allegiance.” Certainly an Act of Congress cannot be invalidated by resting decisive precedents on a gross fiction — a fiction baseless in law and contradicted by the facts of the cases.
It cannot be said, then, that Congress acted without warrant when, pursuant to its power to regulate the relations of the United States with foreign countries, it provided that anyone who votes in a foreign election of significance politically in the life of another country shall lose his American citizenship. To deny the power of Congress to enact the legislation challenged here would be to disregard the constitutional allocation of governmental functions that it is this Court’s solemn duty to guard.
Because of our view concerning the power of Congress with respect to § 401 (e) of the Nationality Act of 1940, we find it unnecessary to consider — indeed, it would be improper for us to adjudicate — the constitutionality of § 401 (j), and we expressly decline to rule on that important question at this time.
Judgment affirmed.