OPINION
FELDMAN, Vice Chief Justice.
Fain Land & Cattle Company (Fain) brought this action against M.J. Hassell, State Land Commissioner (Commissioner), and the Arizona State Land Department (Department) seeking to require the Department to complete an exchange of state school trust lands for privately held lands pursuant to A.R.S. § 37-604 et seq. We must determine whether the transaction permitted by this statute violates the provisions of article 10 of the Arizona Constitution. See Rule 3, Ariz.R.P.Spec.Act., 17B A.R.S. We have jurisdiction under Ariz. Const, art. 6, § 5(1).
FACTS AND PROCEDURAL HISTORY
On September 16, 1985, Fain applied under A.R.S. § 37-604 et seq. to exchange private land it owned for state school trust land. All the land in question is located in Yavapai County. On March 24, 1988, the Commissioner and three members of the State Selection Board approved the exchange of 874 acres owned by Fain for 635 acres of state school trust land. The basis upon which the exchange was approved was that it was “in the interest of the State for reasons of proper management, control, protection or public use of State land” and that “the selected State lands are substantially equal in value.” Petition for Special Action (filed in Sup.Ct. May 31, 1989), at 2. On August 8, 1988, the Department informed Fain that it would not take any further action on the exchange, based on advice from the attorney general’s office that this court’s decision in Deer Valley Unified School Dist. v. Superior Court, 157 Ariz. 537, 760 P.2d 537 (1988), prohibited such exchanges.
On May 19, 1989, counsel for Fain sent a letter to the Commissioner demanding that the Department proceed with the exchange. After the Department refused to proceed on this demand, Fain filed this petition for special action,1 requesting that this court hold that article 10 did not prohibit the exchange of state school trust lands. He also sought an order compelling the Commissioner to complete the exchange.
DISCUSSION
A. Historical Setting: Interplay of the Arizona Enabling Act and Arizona Constitution
In 1910, Congress passed the Arizona-New Mexico Enabling Act, which authorized the residents of those territories to form state governments. Act of June 20, 1910, Pub.L. No. 219 (ch. 310), 36 Stat. 557 (hereafter Enabling Act). Sections 19 through 35 apply to Arizona. One provision of the Enabling Act granted Arizona certain federal land for the purpose of sup[589]*589porting public schools in the new state. Enabling Act § 24. Congress required Arizona to hold the granted land in trust, and only allowed disposal of the trust land subject to very specific and restrictive conditions. See Kadish v. Arizona State Land Dep't, 155 Ariz. 484, 487, 747 P.2d 1183, 1186 (1987), aff'd, — U.S. -, 109 S.Ct. 2037, 104 L.Ed.2d 696 (1989).
The state may only sell or lease trust land to the highest bidder at public auction after public notice. Enabling Act § 28. No sale or other disposal may be made unless the land is first appraised for its “true value,” and the state receives consideration equal to, or greater than, the appraised value. Id. In addition, the Enabling Act provides that any disposition of trust land not in substantial conformity with its provisions is “null and void.” Id. The rationale behind these strict requirements is that prior land grants to other states were improvidently managed, to put it mildly, and Congress wanted to ensure that the legislatures of Arizona and New Mexico would not dissipate the granted land.2 See Kadish, 155 Ariz. at 486-88, 747 P.2d at 1185-87; Murphy v. State, 65 Ariz. 338, 350-53, 181 P.2d 336, 344-46 (1947) (recounting history of abuses that led Congress to insert the restrictions in the Arizona-New Mexico Enabling Act).
The Enabling Act required that the state and its people consent to all its provisions concerning lands granted to the state and that an ordinance be included in the state constitution “in such terms as shall positively preclude the making of any future constitutional amendment or any change or abrogation of the said ordinance in whole or in part without the consent of Congress.” Enabling Act § 20. As a result, the framers inserted the following two clauses in the Arizona Constitution accepting the land grant and agreeing to the restrictions of the Enabling Act:
The State of Arizona and its people hereby consent to all and singular the provisions of the Enabling Act ... concerning the lands thereby granted ... to the State, the terms and conditions upon which said grants and confirmations are made, and the means and manner of enforcing such terms and conditions, all in every respect and particular as in the aforesaid Enabling Act provided.
This ordinance is hereby made a part of the Constitution of the State of Arizona, and no future Constitutional amendment shall be made which in any manner changes or abrogates this ordinance in whole or in part without the consent of Congress.
Ariz. Const, art. 20, Pars. 12 and 13.
In addition, the framers explicitly incorporated the restrictions of section 28 of the Enabling Act pertaining to disposal of trust lands into article 10 of the Arizona Constitution. However, article 10 is not merely a rescript of section 28. The framers added their own provisions for disposal of trust lands. For example, the constitution provides in part:
All lands expressly transferred and confirmed to the State by the provisions of the Enabling Act approved June 20, 1910 ... shall be by the State accepted and held in trust to be disposed of in whole or in part, only in manner as in the said Enabling Act and in this Constitution provided____
Ariz. Const, art. 10, § 1 (emphasis added). This language effectively limits dispositions of state trust land to those authorized by both the Enabling Act and the state constitution.
On February 10, 1911, the people of Arizona ratified the proposed constitution, thus making the Enabling Act part of the organic law of this state. See Deer Valley, 157 Ariz. at 539, 760 P.2d at 539; Kadish, 155 Ariz. at 487, 747 P.2d at 1185; Glad[590]*590den Farms, Inc. v. State, 129 Ariz. 516, 518, 633 P.2d 325, 327 (1981).
From time to time, Congress amended the Enabling Act to allow Arizona greater flexibility in the management and disposal of trust land. Deer Valley, 157 Ariz. at 539, 760 P.2d at 539. In 1934, Congress passed the Taylor Grazing Act, which allowed a state to exchange land located within a federal grazing district for other land. Act of June 28, 1934, ch. 865, 48 Stat. 1269 (codified at 43 U.S.C. §§ 315-316 (1934)). In 1936, Congress amended section 28 of the Enabling Act to permit extended leases and exchanges of school trust land. Act of June 5, 1936, ch. 517, 49 Stat. 1477. The exchange portion of the amendment provided:
The State of Arizona is authorized to exchange any lands owned by it for other lands, public or private, under such regulations as the legislature thereof may prescribe____
Id. (emphasis added). These amendments were intended to liberalize the restrictions on trust lands and allow the state greater freedom to manage the land granted by the Enabling Act. See H.R.Rep. 2615, 74th Cong., 2d Sess. 3 (1936).
In 1937, our state senate considered two concurrent resolutions that would have commenced procedures for amending article 10 of the Arizona Constitution to include the 1936 changes to the Enabling Act. SCR 11 and 12, 13th Legis.Reg.Sess. (1937). Both resolutions died on the calendar. Journal of the Senate, 13th Legis. Reg.Sess. 788 (1937). In 1940, Arizona amended article 10 to include the leasing provisions of the 1936 amendment to the Enabling Act, but did not incorporate the exchange provisions. Ariz. Const, art. 10, § 3 (amendment approved election Nov. 5, 1940, eff. Nov. 27, 1940). The 1936 Enabling Act amendment permitting exchanges has never been incorporated into the Arizona Constitution.
In 1948, without commencing the process for amending the constitution, the state legislature adopted the exchange terms of the Taylor Grazing Act and the broader 1936 exchange amendment. 1948 Ariz. Sess.Laws 633-34 (codified at A.R.S. § 11-1211 (1948)). The legislature ratified all prior land exchanges and passed a law that allowed the land department to exchange school trust land for federal land. Id. In 1971, the legislature enacted A.R.S. § 37-604 et seq., which authorized exchanges of state land, including school trust lands, for private lands.3 These statutes have no provision for notice and public auction. The exchange proposed in the present case is to be made, therefore, without public auction.
The attorney general formulates the following issue for our consideration: May the state enter into exchange transactions without complying with the public auction requirement of the Arizona Constitution when the transaction is permitted by state statutes passed under the authority of the Enabling Act?
B. Impact of Deer Valley on Land Exchanges
1. Two Levels of Protection
In Deer Valley, this court held that a school district could not condemn state trust lands for school purposes. Deer Valley, 157 Ariz. at 541, 760 P.2d at 541. The Deer Valley school district wanted to obtain a particular parcel of trust land on which to build a new elementary school. The Department refused to hold a public auction and allow the school district an opportunity to purchase the property. Deer Valley then attempted to condemn the proposed site under the eminent domain provisions of A.R.S. § 12-1111 et seq. The trial court dismissed the complaint on the grounds that the proposed condemnation violated both the Enabling Act and the Arizona Constitution. The appeal was transferred to this court to consider whether either the Enabling Act or the Arizona Constitution allowed a school district to condemn trust land. We held that the Ari[591]*591zona-New Mexico Enabling Act did not prevent acquisition of school trust property by condemnation, but the Arizona Constitution did.
We based our decision in Deer Valley on the premise that because Arizona included the restrictions on disposal of state trust land in its constitution, and because art. 10, § 1 requires that trust land be disposed of “only as provided in the Enabling Act and in the state constitution,” there exist “two complementary levels of protection against improvident state legislative or executive disposal of Arizona’s school trust land.” 157 Ariz. at 539-40, 760 P.2d at 539-40. Both levels of protection must be satisfied for any disposal of state trust land to be valid. Id. We concluded that the Enabling Act provides a minimum level of protection for trust land, while our state constitution goes much further. Id. at 541, 760 P.2d at 541. The Arizona Constitution plainly requires that school trust land be disposed of only after public notice, auction, and sale to the highest and best bidder. Ariz. Const, art. 10, § 3.. The Enabling Act may permit disposal by condemnation. See Lassen v. Arizona ex rel. Arizona Highway Dep’t, 385 U.S. 458, 87 S.Ct. 584, 17 L.Ed.2d 515 (1967). Nonetheless, we concluded that the express provisions of article 10 prohibit methods of disposal not enumerated in our constitution. Deer Valley, 157 Ariz. at 541, 760 P.2d at 541. After Deer Valley, the Department suspended any further land exchanges pending clarification of the impact of the decision on exchanges.
2. Is an Exchange a Sale?
Emphasizing that condemnation is a forced sale without public auction, therefore violating both the Enabling Act and the Arizona Constitution, Fain contends that an exchange is not a sale. Because exchanges are explicitly authorized by the Enabling Act and not expressly prohibited by the Arizona Constitution, Fain argues that Deer Valley is not applicable to exchanges.
In Deer Valley, we said “[o]ur state charter plainly says that the state may not sell, lease or otherwise dispose of school trust land other than to the highest and best bidder at a duly advertised public auction.” 157 Ariz. at 540, 760 P.2d at 540 (quoting Ariz. Const, art. 10, §§ 3-4). Fain accurately points out that the public auction provision of section 3 applies only to sales and leases, not all disposals, and only the appraisal provision of section 4 applies to all disposals. Thus, we must define an exchange and determine whether it differs from a sale. We also must determine whether the word “sale” in the Enabling Act and/or the Arizona Constitution encompasses an exchange.
A generally accepted definition of exchange is a “reciprocal transfer of property for other property of value, rather than for a money consideration.” 30 AM.JUR.2d Exchange of Property § 1, at 363 (2d ed. 1967); see also 33 C.J.S. Exchange of Property § 1, at 4 (1942). Although a technical distinction exists between a sale and an exchange of property, the result is the same. Both transfer legal title from one party to another. In fact, the term “exchange” may be construed to be a form of sale. See 30 AM.JUR.2d Exchange of Property § 3, at 365-66.
Courts in other jurisdictions have distinguished exchanges from sales of real property. The key appears to be that an exchange occurs only if no value is assigned to either of the exchanged properties. See, e.g., Gruver v. C.I.R., 142 F.2d 363, 366 (D.C.Cir.1944) (transaction is an exchange if the parties set no price for the property); Ashton v. Ashton, 89 Ariz. 148, 153, 359 P.2d 400, 403 (1961) (where the consideration for a transfer of property is expressed or valued in money terms the transaction is a sale); Herring Motor Co. v. Aetna Trust & Sav. Co., 87 Ind.App. 83, 154 N.E. 29, 31 (1926) (transaction is an exchange where the parties transfer two properties without setting a price for either one); Griswold v. Tucker, 216 S.W.2d 276, 278 (Tex.Civ.App. 1948) (exchange occurs if one party passes property to another and receives property in return without any agreed upon value assigned to the property). The commonly accepted definition of “exchange” excludes transactions into which money enters, either as the consideration furnished by one [592]*592party or as a basis for measuring the value of the property transferred. See, e.g., Trenton Cotton Oil Co. v. C.I.R., 147 F.2d 33, 36 (6th Cir.1945); Badgett v. United States, 175 F.Supp. 120, 126 (D.C.Ky.1959); Gill v. Eagleton, 108 Neb. 179, 187 N.W. 871, 872 (1922); Hoovel v. State, 125 Tex. Crim. 545, 69 S.W.2d 104, 108 (1934).
Thus, the test for determining whether a transaction constitutes a sale or an exchange is whether there is a fixed value at which the exchange is to be made—it is considered a sale if there is a fixed value and an exchange if there is not. Hawn v. Malone, 188 Iowa 439, 176 N.W. 393, 395 (1920). The rationale of these and other cases is succinctly and accurately summarized as follows:
[W]here the parties exchange one property for another and the price or the value is not measured in terms of money, the transaction is an exchange, but if the property is disposed of for a valuable consideration with or without the payment of money and the bargain is made, and the value is measured, in terms of money, the transaction is a sale.
30 AM.JUR.2d Exchange of Property § 3, at 365.
Under the terms of the Enabling Act and our constitution, state trust land must be appraised prior to any disposal. This mandatory appraisal in effect sets a monetary value for the trust land to be conveyed. That “true value” must be obtained on disposal. Enabling Act § 28. Consequently, any disposition of trust land is based on realizing a preset dollar value and therefore results in a sale rather than an exchange.4 We conclude, therefore, that an exchange of state trust land based on its appraised monetary value is a form of sale, even though the consideration is received in kind and not in cash. Given the restrictions the constitution places on all disposals, any exchange would effectively constitute a sale.
The dissent argues that the transaction in question here was merely “a transfer of property for property” and not a sale because there was “no definite value” fixed on the state land, “money [was not] used as the basis of measure,” and no “fixed price [was] required” by law. Dissent at 45, 47, 48-49, 51. The dissent overlooks the Enabling Act requirement that all trust “lands ... shall be appraised at their true value, and no sale or other disposal thereof shall be made for ... less than the value so ascertained.” Enabling Act § 28, 1 A.R.S. at 109 (first full paragraph). Thus, before the state can dispose of trust land, it must ascertain a definite value by appraisal and obtain a consideration at least equal to that value. The same restrictions are in the Arizona Constitution in article 10, § 4. Contrary to the view of the dissent, therefore, the Enabling Act requires that a definite monetary value or price be fixed as the basis for the transfer.
C. The Exchange Statutes and the Arizona Constitution
The Enabling Act, as amended, clearly permits Arizona to authorize exchanges of public trust lands. Having concluded that the exchange is a sale, we must now determine whether the Arizona Constitution prohibits the exchange procedure created by the Arizona statutes.
In 1971, the Arizona legislature enacted a statutory framework authorizing the Department to exchange all state land, including school trust land, for public or private land. A.R.S. § 37-604 et seq. This framework requires the Department to carefully consider any proposed exchange of trust land. Some of the requirements of this statutory scheme include a determination by the Department “that the proposed exchange would benefit the applicable trust”; [593]*593at least two independent appraisals that determine the value of the land offered for exchange to be substantially equal in value or worth more than the state land to be exchanged; notice in writing to other interested state agencies, counties, municipalities, and leaseholders on state lands that may be affected by the exchange; published notice of all proposed exchanges in the same manner required for sales of trust land; a public hearing on the exchange; dedication of the land conveyed to the state to the same purpose as the land exchanged; and provisions for protest, public hearing, and appeal of exchanges of trust land. Id.
Although this scheme provides many safeguards against improvident disposal of trust land, it does not provide all the protections of the original Enabling Act or article 10 of the Arizona Constitution. Most notably missing is the requirement of sale to the highest bidder at public auction. The purpose of this provision is to ensure that the trust receives the most benefit possible from sale or other use of the trust lands. See Comment, Arizona’s Enabling Act and the Transfer of State Lands for Public Purposes, 8 ARIZ.L.REV. 133, 134 (1966). Without sale at public auction, the trust is not guaranteed the additional profit that might result from competitive bidding. Deer Valley, 157 Ariz. at 540, 760 P.2d at 540. It certainly is conceivable that someone might bid more than the appraised price at a public auction for a particularly desirable parcel, see Gladden Farms, 129 Ariz. at 520, 633 P.2d at 329, whereas with an exchange, the state is guaranteed only the appraised value of the property. We hold, therefore, that as applied to land held in the school trust, A.R.S. § 37-604 et seq. do not comply with article 10, § 3 of the Arizona Constitution. Because the constitution requires all sales to be at public auction, and because an exchange made for a preset appraised monetary value is a form of sale, no exchanges are permitted by the Arizona Constitution.
D. Does the Enabling Act Effectively Amend the Arizona Constitution?
Fain argues that by consenting to the terms of the original Enabling Act, Arizona in effect consented to any future amendments of the act. Fain correctly cites as a settled principle of statutory construction the rule that amendments to a statute should be construed as if they were part of the original act. See 1A N. SINGER, SUTHERLAND STATUTORY CONSTRUCTION § 22.35, at 296 (4th ed. 1985). However, this case does not involve a question of statutory construction. If the amended provisions of the Enabling Act were our only concern, we would conclude that A.R.S. § 37-604 et seq. could validly be applied to school trust land. We are also required, however, to read and apply the provisions of our state constitution, which unambiguously require sale at public auction. No constitutional authority exempts sales of trust land simply by calling them exchanges and allowing the state to accept payment in kind instead of cash.
Thus, we cannot agree with the dissent’s view that exchanges are simply transfers of property for property and therefore exempt from the public auction requirements of the constitution. If this were so, the restrictions of the original Enabling Act would have been useless, for the state could have disposed of the trust lands simply by transfers in kind. Nor would such an interpretation comport with the understanding of Congress. If Congress had intended to exempt exchanges from the public auction requirements of the Enabling Act and the Arizona Constitution, there would have been no need for our legislature to petition Congress to amend the Enabling Act {see post n. 5), nor any need for Congress to pass the amendment, thereby authorizing Arizona to permit exchanges, if it so desired, by amending its constitution.
Nor do we believe that by consenting to the provisions of the Enabling Act, and presumably to its amendments, the people of Arizona intended to cede to Congress the power to amend the state constitution. Fain’s suggestion that amendments to the Enabling Act should be construed as if they were part of the original act and therefore part of the Arizona Constitution would effectively grant Congress that pow[594]*594er. Such a delegation would directly conflict with the provision that the people of the state reserve the power to propose amendments to the constitution and to enact or reject those amendments, independent of the legislature. Ariz. Const, art. 4, pt. 1, § 1(1). Surely, if the framers deprived the state’s legislature of the power to amend the state’s constitution, they cannot have intended to delegate it to Congress. Nor would such an intention have been consistent with our founders’ concept of the federal-state relationship. Leshy, The Making of the Arizona Constitution, 20 ARIZ.ST.L.J. 1 (1988).
We are mindful that Congress, the set-tlor of the trust, has granted permission for the state, as trustee, to permit exchanges on such terms as the legislature determines are proper. We are mindful also that the legislature has enacted a statute that permits exchanges to be consummated only on many conditions designed to protect the public interest. So far as this record shows, the exchange proposed by Fain and agreed upon by the Department complies with the statute in all respects. It is tempting, of course, under such conditions, to approve the legislative scheme. However, constitutional principles and jurisprudential considerations prevent us from ignoring the plain, unambiguous text of our constitution.
The framers of our constitution were not required to insert the original provisions of the Enabling Act in the state constitution, but consciously chose to do so. When the people of Arizona voted on and accepted the constitution, with the provisions of the Enabling Act included, they obviously intended the words so adopted to become part of the organic law of this state. Indeed, the territorial delegates to Congress, Robert E. Morrison, Ralph H. Cameron, and J. Lorenzo Hubbell, all testified to the senate committee that the people of this state approved the original provisions of the Enabling Act in their entirety. See Report of Senator Beveridge, Chairman of the Committee on Territories (Senate Comm, on Territories, Report 454, 61st Congress, Second Session).
We conclude, therefore, that the amendments to the Enabling Act have not effected an amendment to the Arizona Constitution. The textual provisions of the Arizona Constitution prohibiting sale except by public auction are still in effect and must be applied, unless the amendments to the Enabling Act can be said to have preempted the contrary provisions of the Arizona Constitution.
E. Preemption
Fain argues next that even if we interpret the Arizona Constitution to prohibit exchanges of school trust land, such restriction is preempted by the 1936 amendment to the Enabling Act. Fain correctly points out that state constitutions may be preempted by federal law. See U.S. Const, art. 6, cl. 2 (“This Constitution, and the Laws of the United States which shall be made in pursuance thereof ... shall be the supreme Law of the Land ... any Thing in the Constitution or Laws of any State to the Contrary notwithstanding.”); see also Developments in the Law—The Interpretation of State Constitutional Rights, 95 HARV.L.REY. 1324, 1338 (1982). The supremacy clause mandates that federal law preempts state law where there is an actual conflict between the two. 1 R. ROTUNDA, J. NOWAK, J. YOUNG, TREATISE ON CONSTITUTIONAL LAW: SUBSTANCE AND PROCEDURE § 12.1, at 623 (1986).
We have previously acknowledged that the Enabling Act is superior to the Arizona Constitution. See, e.g., Radish, 155 Ariz. at 486, 747 P.2d at 1185 (“Because federal law is supreme in this field, neither this court, nor the legislature, nor the people may alter or amend the trust provisions contained in the Enabling Act without congressional approval.”); Gladden Farms, 129 Ariz. at 518, 633 P.2d at 327; Murphy, 65 Ariz. at 345, 181 P.2d at 340 (“The Arizona Constitution cannot be inconsistent with the Enabling Act.”); Boice v. Campbell, 30 Ariz. 424, 428, 248 P. 34, 35 (1926).
However, in this case, no direct, actual conflict exists between the Enabling Act and the Arizona Constitution. By includ[595]*595ing the restrictions on disposal of trust land in its constitution, Arizona does not require an act that federal law forbids. See R. ROTUNDA, supra, § 12.6, at 623. It merely provides additional protection to the trust lands, which it may legitimately do. Id., § 1.6, at 31 (“[S]tate courts are always free to grant individuals more rights than those guaranteed by the Constitution, provided [they] do so on the basis of suite law.”).
Generally, without clear evidence of congressional intent, a federal law will not preempt state regulations. Id., § 12.6, at 623. The exchange amendment and its legislative history do not suggest any intent on the part of Congress to preempt Arizona’s constitution. By passing the 1936 amendment, Congress merely consented to removal of the restrictions against exchange of trust land, but did not require Arizona to amend its constitution or to pass legislation to allow exchanges.5 The language of the amendment is permissive only. It states that Arizona “is authorized” to permit exchanges under such rules as the legislature may provide. Act of June 5, 1936, ch. 517, 49 Stat. 1477. Because the grant of power in the exchange amendment is permissive, no actual conflict exists between it and the Arizona Constitution.
Moreover, the provisions of article 10 do not “stand[ ]■ as an obstacle to the accomplishment and execution of the full purposes and objectives of Congress.” Pacific Gas & Elec. v. State Energy Resources Conservation & Dev. Comm’n, 461 U.S. 190, 203-04, 103 S.Ct. 1713, 1722, 75 L.Ed.2d 752 (1983). The purpose of the Enabling Act restrictions on disposal of trust land is to ensure that the trust receives the most benefit possible from the trust lands. The purpose of the restrictions in article 10 of our constitution is the same—the restrictions do not frustrate the purposes of the Enabling Act.
The cardinal rule of constitutional construction is to follow the text and the intent of the framers, where it can be ascertained. See, e.g., County of Apache v. Southwest Lumber Mills, Inc., 92 Ariz. 323, 327, 376 P.2d 854, 856 (1962) (“The governing principle of constitutional construction is to give effect to the intent and purpose of the framers of the constitutional provision and of the people who adopted it.”). In the case before us, we are compelled to conclude that the provisions of the Arizona Constitution must be applied. The statutes, A.R.S. §§ 37-604 to 37-607, cannot be constitutionally applied to permit the sale—even if it be called an exchange—of school trust lands without compliance with the provisions of article 10 of the Arizona Constitution, including those provisions of section 3 that require that the state land be placed at public auction and sold to the highest bidder. In order for Arizona to legitimately permit exchanges of school trust land, it must amend the state constitution, as well as enact a statute setting forth the proper procedure.
For the foregoing reasons, we hold that the 1936 amendment to the Enabling Act does not preempt the provisions of article 10 of the Arizona Constitution.
F. Validity of Past Exchanges—Constitutional Nullification
Although the validity of past exchanges is not directly before us at this time, Fain argues that a decision by this court that the legislature lacks the constitutional authority to permit exchanges of school trust land could have potentially grave ramifications regarding the status of past ex[596]*596changes. Although ordinarily the retroactive effect of this decision could be left for determination in a future case, we believe it would be unwise for this court to cloud the title to thousands of acres of land conveyed and reconveyed in past exchanges. We must therefore decide the issue of re-troactivity at this juncture.
Article 10, § 1 of our constitution permits disposition of school trust lands only in the manner provided by the Enabling Act and the Arizona Constitution. What is the result if trust land is disposed of in a way that does not violate provisions of the Enabling Act but does violate the Arizona Constitution? Section 28 of the Enabling Act provides:
Every sale, lease, conveyance, or contract of or concerning any of the lands hereby granted or confirmed, ... not made in substantial conformity with the provisions of this Act shall be null and void, any provisions of the constitution or laws of the said State to the contrary notwithstanding____
(Emphasis added.) Article 10, § 8 of the Arizona Constitution contains an important difference; it provides:
Every sale, lease, conveyance, or contract of or concerning any of the lands granted or confirmed ... not made in substantial conformity with the provisions [of the Enabling Act], shall be null and void.
(Emphasis added.)
These provisions of our constitution do not nullify all dispositions of trust land not made in strict compliance with article 10 of our constitution. The only dispositions of trust land that are nullified are those that do not comply with the Enabling Act. The Enabling Act as amended authorizes Arizona to pass legislation providing for exchanges of trust land. Arizona has done so. Therefore, exchanges completed pursuant to A.R.S. § 37-604 et seq. comply with the Enabling Act, and we are not required by the text of our constitution to nullify past exchanges. The validity of completed exchanges must turn on the question of the retroactivity of this opinion.
G. Retroactive Versus Prospective Application of this Decision
Whether an opinion will be given prospective application only is a policy question within this court’s discretion. See Hawkins v. Allstate Ins. Co., 152 Ariz. 490, 505, 733 P.2d 1073, 1088, cert. denied, 484 U.S. 874, 108 S.Ct. 212, 98 L.Ed.2d 177 (1987). In Arizona, unless otherwise specified, an opinion in a civil case operates retroactively as well as prospectively. See Law v. Superior Court, 157 Ariz. 147, 160, 755 P.2d 1135, 1148 (1988); Mark Lighting Fixture v. General Elec. Supply Co., 155 Ariz. 27, 30, 745 P.2d 85, 88 (1987); Hawkins, 152 Ariz. at 504, 733 P.2d at 1087; Brannigan v. Raybuck, 136 Ariz. 513, 520, 667 P.2d 213, 220 (1983); Chevron Chem. Co. v. Superior Court, 131 Ariz. 431, 435, 641 P.2d 1275, 1279 (1982). In Chevron Chemical, we approved a three-part test to determine whether this presumption of retroactivity has been overcome and a decision should be applied prospectively only. 131 Ariz. at 436, 641 P.2d at 1280. The factors to be considered are:
1. Whether the decision establishes a new legal principle by overruling clear . and reliable precedent or by deciding an issue whose resolution was not foreshadowed;
2. Whether retroactive application will further or retard operation of the rule, considering the prior history, purpose, and effect of the rule;
3. Whether retroactive application will produce substantially inequitable results.
Mark Lighting, 155 Ariz. at 30, 745 P.2d at 88. These factors have been termed the reliance, purpose, and inequity factors. Hawkins, 152 Ariz. at 504, 733 P.2d at 1087.
The case law has not always been clear whether all factors must favor prospective application, or whether retroactive application is inappropriate if a single factor favors prospective application. Mark Lighting, 155 Ariz. at 31, 745 P.2d at 89; Hawkins, 152 Ariz. at 505, 733 P.2d at 1088. However, in Law, we settled the issue, reasoning that “[t]he decision of whether [597]*597an opinion will only be applied prospectively involves a balancing of these three factors,” and concluding that our decision in that case should have prospective effect only, based on two of the three factors. 157 Ariz. at 161-62, 755 P.2d at 1149-50.
1. The Reliance Factor
In this case, we are deciding an issue whose resolution was certainly not foreshadowed. The state has engaged in land exchanges for many years under the assumption that valid statutory authorization existed. Although there have been other court cases dealing with exchanges of state trust lands, the issue of the constitutionality of such exchanges did not arise. It was not until our decision in Deer Valley that this assumption was called into question. Therefore, our decision in this case was not clearly foreshadowed by Arizona caselaw decided before Deer Valley, and this factor weighs against retroactive operation of our holding in this case.
2. The Purpose Factor
In this case, it is not entirely clear whether the balance on this factor weighs in favor of prospective application only. Essentially, our decision is based on the principle that the explicit terms of the Arizona Constitution must be followed. Applying this decision retroactively would not impair the purpose of the rule and might further its purpose by deterring violation. On the other hand, the statutory authorization for land exchanges, although passed without proper constitutional authority, contains significant restrictions on disposal, all of which are designed to fulfill the state’s fiduciary responsibility. Ketroactive application of this decision would not violate the trust because Congress has allowed exchanges. In this case, the purpose of the rule is not affected by its prospective or retroactive application, and the balance on this factor is neutral.
3. The Inequity Factor
This factor focuses on the injustice or hardship that would result from retroactive application of the new rule. See Peagler v. Phoenix Newspapers, 114 Ariz. 309, 313, 560 P.2d 1216, 1220 (1977). Where a decision of this court could produce a substantially inequitable result if applied retroactively, we may avoid the injustice or hardship by applying the decision prospectively only. See Law, 157 Ariz. at 161, 755 P.2d at 1149. The balance of equities on this factor tips strongly in favor of prospective application only. Several hundred land exchanges have been completed over the years, affecting thousands of acres. If applied retroactively, this opinion might inflict great hardship on many innocent people, and perhaps disrupt the economy of the state. It would be impossible to undo all the land exchanges that have transpired and put everyone back in his original position.
Giving consideration to the above factors, we conclude that the balance weighs heavily in favor of limiting the effect of this decision to prospective application. Therefore, exchanges accomplished in compliance with the state’s fiduciary obligations and with the 1936 exchange amendment to the Enabling Act and prior to the date of the opinion in Deer Valley are not void.
CONCLUSION
The Arizona Constitution limits the disposal of state trust lands solely to the methods provided in the Enabling Act and the Arizona Constitution. As we stated in Deer Valley, the Enabling Act provides a minimum level of protection of state trust land. Arizona has provided a heightened level of protection by incorporating the restrictions on disposal of trust land directly into its constitution. No authorization for exchanges of trust land exists in the Arizona Constitution. The amendment to the Enabling Act that allows exchanges of school trust land was never incorporated into the Arizona Constitution. An exchange at a predetermined, approved dollar value is a sale. The Arizona Constitution requires that all sales be made at public auction. Therefore, no constitutional authority exists for the legislature to authorize exchanges. As a result, we find that [598]*598the statutory scheme regulating exchanges of state land found in A.R.S. §§ 37-604 to 37-607 is unconstitutional as applied to school trust land.
Because of the severe consequences that would result if this opinion were applied retroactively, we hold that this opinion shall be applied prospectively only, from the date on which Deer Valley was decided.
GORDON, C.J., and MOELLER, J., concur.