MR. CHIEF JUSTICE BURGER delivered the opinion of the Court.

We granted the writ in this case to consider whether state law may retroactively abrogate the terms of written agreements made by the United States when it acquires land for public purposes explicitly authorized by Congress.

The United States initiated this litigation in 1969 in the United States District Court for the Western District of Louisiana, seeking to quiet title to two adjacent parcels of land in Cameron Parish, Louisiana, which the Government had acquired pursuant to the Migratory Bird Conservation Act, 45 Stat. 1222, 16 U.S.C. § 715 et seq., as part of the Lacassine Wildlife Refuge. Title to one parcel was acquired by the United States by purchase on July 23, 1937; to the other parcel by a judgment of condemnation entered August 30, 1939. Both the 1937 act of sale and the 1939 judgment of condemnation reserved to the respondent Little Lake Misere oil, gas, sulphur, and other minerals for a period of 10 years from the date of vesting of title in the United States. The reservation was to continue in effect "as long [after the initial ten-year period] as oil, gas, sulphur or other mineral is produced . . . or so long thereafter as [respondents] shall conduct drilling or reworking operations thereon with no cessation of more than sixty (60) days consecutively until production results; and, if production results, so long as such mineral is produced." The deed and the judgment of condemnation further recited that at the end of 10 years or at the end of any period after 10 years during which the above conditions had not been met, "the right to mine, produce and market said oil, gas, sulphur or other mineral shall terminate . . . and the complete fee title to said lands shall thereby become vested in the United States."

The parties stipulated, and the District Court found, that as to both the parcels in issue here, no drilling, reworking, or other operations were conducted and no minerals were obtained for a period of more than 10 years following the act of sale and judgment of condemnation, respectively. Thus, under the terms of these instruments, fee title in the United States ripened as of 1947 and 1949, respectively — 10 years from the dates of creation. In 1955, the United States issued oil and gas leases applicable to the lands in question.

Respondents, however, continued to claim the mineral rights and accordingly entered various transactions purporting to dispose of those rights. Respondents relied upon Louisiana Act 315 of 1940, La. Rev. Stat. § 9:5806 A (Supp. 1973), which provides:

"When land is acquired by conventional deed or contract, condemnation or expropriation proceedings by the United States of America, or any of its subdivisions or agencies from any person, firm or corporation, and by the act of acquisition, order or judgment, oil, gas or other minerals or royalties are reserved, or the land so acquired is by the act of acquisition conveyed subject to a prior sale or reservation of oil, gas or other minerals or royalties, still in force and effect, the rights so reserved or previously sold shall be imprescriptible."

Respondents contended that the 1940 enactment rendered inoperative the conditions set forth in 1937 and 1939 for the extinguishment of the reservations. The District Court concluded that the Court of Appeals' prior decision in Leiter Minerals, Inc. v. United States, 329 F.2d 85 (CA5 1964), required resolution of this case in favor of respondents, notwithstanding that we had vacated the Court of Appeals' judgment in Leiter Minerals and remanded with instructions to dismiss the complaint as moot. 381 U.S. 413 (1965). The Court of Appeals affirmed, for the reasons stated in its Leiter Minerals holding. It rejected the Government's Contract Clause and Supremacy Clause objections on the authority of United States v. Nebo Oil Co., 190 F.2d 1003 (CA5 1951), and further rejected the Government's argument that Act 315 was unconstitutionally discriminatory against the United States. The Court of Appeals observed "that the same principle applies to acquisitions by the State of Louisiana [La. Rev. Stat. § 9:5806 B], and that the act really does nothing more than place citizens of Louisiana in the same position as citizens of other states whose land has been purchased or condemned by the United States." 453 F.2d 360, 362 (1971). We reverse.

I

Litigation involving Act 315 began more than a quarter century ago. The Leiter Minerals case, upon which the Court of Appeals based its decision in this case, is only the principal holding in the area. The first case to arise involving Act 315, Whitney Nat. Bank v. Little Creek Oil Co., grew out of a 1932 sale of mineral rights that specified a 10-year period of prescription. The surface property was conveyed to the United States in 1936, subject to the 1932 mineral sale, and in 1947 the question arose whether Act 315 of 1940 had the effect of extending indefinitely the servitude created by the 1932 sale. The Louisiana Supreme Court held that Act 315 of 1940 was fully applicable to the 1936 transaction — "not because there is anything in the terms of the statute to indicate that it was intended to have a retroactive application, but because of the general rule of law established by the jurisprudence of this court that laws of prescription and those limiting the time within which actions may be brought are retrospective in their operation." 212 La. 949, 958, 33 So.2d 693, 696 (1947). The court acknowledged the contention that if Act 315 were applied retroactively, it might be unconstitutional, but dismissed the constitutional issue without resolving it for failure to join the United States, a necessary party.

Whitney Bank set the stage for the first federal court test of Act 315, as construed to have retroactive application, in United States v. Nebo Oil Co., supra, aff'g 90 F. Supp. 73 (WD La. 1950). There the United States brought suit against Nebo Oil (the successor to the 1932 mineral purchaser of the Whitney Bank case) to secure a declaratory judgment that the United States owned the acreage it purchased in 1936 subject only to the 10-year rule of prescription specified at the time of the original 1932 sale of mineral rights. But the Court of Appeals upheld the application of Act 315 to the previously consummated transaction, stressing that reversionary estates are unknown in Louisiana law and that, as a result, the United States in 1936 took "nothing more than a mere expectation, or hope, based upon an anticipated continuance of the applicable general laws . . . . [This] mere expectancy . . . cannot be regarded as a vested right protected by the Constitution." 190 F.2d, at 1008-1009.

In the Leiter Minerals litigation, retrospective application of Act 315 to a detailed, conditional mineral reservation was in issue for the first time. Leiter Minerals, Inc., succeeded to the interests of the Leiter family, which in 1938 had sold a substantial tract in Plaquemines Parish, Louisiana, to the United States. Leiter's federal sale was subject to a mineral reservation in Leiter's favor, providing in essence that the reservation would be extended for five years beyond its initial 10-year duration whenever commercially advantageous mineral extraction had occurred during 50 days of a defined period. At the expiration of any period during which the conditions for extension had not been met, the right to mine would terminate "and complete fee in the land becomes vested in the United States." The mineral reservation expired by its own terms; the Government granted a valuable mineral lease; and Leiter invoked Act 315 to support its claim to a servitude of continuing duration.

After a false start in the Louisiana courts, the ensuing litigation found its way into a federal forum. The United States sued in the Eastern District of Louisiana to quiet title and to enjoin the concurrent state court proceedings initiated by Leiter. The Court of Appeals affirmed an injunction granted by the District Court, and this Court agreed, but remanded to the Court of Appeals with instructions to secure an authoritative construction of Act 315 before proceeding to the difficult constitutional issues in the case. Leiter Minerals, Inc. v. United States, 352 U.S. 220, 229 (1957).

Adhering to the terms of the remand, Leiter sought a declaratory judgment in the Louisiana courts, which expressed some continuing doubt over the breadth of their responsibility for resolving the Leiter controversy on its own facts. Ultimately, the Louisiana Supreme Court took jurisdiction of the case and rendered a declaratory judgment limited to general elucidation of Act 315, without applying the Act to the specific terms of the Leiter mineral reservation itself. Leiter Minerals, Inc. v. California Co., 241 La. 915, 132 So.2d 845 (1961). The Louisiana Supreme Court expressed its conclusions as follows:

"First, that if the reservation in the Leiter deed is construed as establishing a mineral servitude for a definite, fixed, and specified time which has elapsed, then Act 315 of 1940 is not applicable and cannot be constitutionally applied; and second, that if the reservation is construed as not establishing a servitude for a fixed, definite and certain time, and if it is decided that the provisions of the reservation show that the parties were stipulating for a period of contractual prescription for the conditional extinguishment of the mineral servitude created, then Act 315 of 1940 is applicable and constitutional." Id., at 942, 132 So.2d, at 854-855.

Recognizing that "the interpretation of this reservation is for the United States courts, and not for us in this proceeding." id., at 930, 132 So.2d, at 850, that court nevertheless hinted broadly that it viewed the Leiter reservation as one establishing a reservation for an indefinite period of time, and thus one subject to retroactive application of Act 315. See id., at 936, 938, 132 So.2d, at 852, 853.

The parties then returned to federal court. The District Court held that the mineral reservation in the Leiter deed created a mineral servitude for a fixed period and that, under the terms of the Louisiana Supreme Court's declaratory ruling, as a matter of state law the reservation was not affected by Act 315. 204 F. Supp. 560 (ED La. 1962). The Court of Appeals reversed. It rejected the Government's contention that federal law controlled the rights of the United States under the reservation, and held, instead, that those rights were to be governed by Louisiana law. The Court of Appeals believed that the Louisiana Supreme Court had viewed Leiter's servitude as "one of indefinite duration" and it agreed with that view. Under Louisiana law, therefore, the reservation "provide[d] for a contractual prescription for the conditional extinguishment of the mineral servitude which was rendered inoperative by [Act 315]." 329 F.2d, at 93. As to the Government's contention that the Act, as so construed, unconstitutionally impaired the obligation of contract, the Court of Appeals concluded that the discussion of that matter in its prior decision in Nebo Oil, supra, and in the Louisiana Supreme Court's Leiter opinion, made it "unnecessary further to labor" the point. Id., at 94. Judge Gewin dissented. On being advised by the parties that the case had been settled, we granted certiorari, vacated the judgment of the Court of Appeals, and remanded the cause to the District Court with instructions to dismiss the complaint as moot. 381 U.S. 413 (1965).

II

The essential premise of the Court of Appeals' decision in the Leiter Minerals case was that state law governs the interpretation of a federal land acquisition authorized by the Migratory Bird Conservation Act. The Court of Appeals did not set forth in detail the basis for this premise, but that court's opinion seems to say that state law governs this land acquisition because, at bottom, it is an "ordinary" "local" land transaction to which the United States happens to be a party. The suggestion is that this Court's decision in Erie R. Co. v. Tompkins, 304 U.S. 64 (1938), compels application of state law here because the Rules of Decisions Act, 28 U.S.C. § 1652, requires application of state law in the absence of an explicit congressional command to the contrary. We disagree.

The federal jurisdictional grant over suits brought by the United States is not in itself a mandate for applying federal law in all circumstances. This principle follows from Erie itself, where, although the federal courts had jurisdiction over diversity cases, we held that the federal courts did not possess the power to develop a concomitant body of general federal law. Mishkin, The Variousness of "Federal Law": Competence and Discretion in the Choice of National and State Rules for Decision, 105 U. Pa. L. Rev. 797, 799 (1957). It is true, too, that "[t]he great body of law in this country which controls acquisition, transmission, and transfer of property, and defines the rights of its owners in relation to the state or to private parties, is found in the statutes and decisions of the state." Davies Warehouse Co. v. Bowles, 321 U.S. 144, 155 (1944). Even when federal general law was in its heyday, an exception was carved out for local laws of real property. Swift v. Tyson, 16 Pet. 1, 18 (1842); see Kuhn v. Fairmont Coal Co., 215 U.S. 349, 360 (1910). Indeed, before Erie R. Co. v. Tompkins, supra, this Court's opinions left open the possibility that even "the United States, while protected by the Constitution from discriminatory state action, and perhaps certain other special forms of state control, was nevertheless governed generally in its ordinary proprietary relations by state law." Hart, The Relations Between State and Federal Law, 54 Col. L. Rev. 489, 533 (1954). See, e.g., Mason v. United States, 260 U.S. 545, 558 (1923).

Despite this arguable basis for its reasoning the Court of Appeals in the instant case seems not to have recognized that this land acquisition, like that in Leiter Minerals, is one arising from and bearing heavily upon a federal regulatory program. Here, the choice-of-law task is a federal task for federal courts, as defined by Clearfield Trust Co. v. United States, 318 U.S. 363 (1943). Since Erie, and as a corollary of that decision, we have consistently acted on the assumption that dealings which may be "ordinary" or "local" as between private citizens raise serious questions of national sovereignty when they arise in the context of a specific constitutional or statutory provision; particularly is this so when transactions undertaken by the Federal Government are involved, as in this case. In such cases, the Constitution or Acts of Congress "require" otherwise than that state law govern of its own force.

There will often be no specific federal legislation governing a particular transaction to which the United States is a party; here, for example, no provision of the Migratory Bird Conservation Act guides us to choose state or federal law in interpreting federal land acquisition agreements under the Act. But silence on that score in federal legislation is no reason for limiting the reach of federal law, as the Court of Appeals thought in Leiter Minerals. To the contrary, the inevitable incompleteness presented by all legislation means that interstitial federal lawmaking is a basic responsibility of the federal courts. "At the very least, effective Constitutionalism requires recognition of power in the federal courts to declare, as a matter of common law or 'judicial legislation,' rules which may be necessary to fill in interstitially or otherwise effectuate the statutory patterns enacted in the large by Congress. In other words, it must mean recognition of federal judicial competence to declare the governing law in an area comprising issues substantially related to an established program of government operation." Mishkin, 105 U. Pa. L. Rev., at 800.

This, then, is what has aptly been described as the "first" of the two holdings of Clearfield Trust Co. v. United States, supra — that the right of the United States to seek legal redress for duly authorized proprietary transactions "is a federal right, so that the courts of the United States may formulate a rule of decision." Friendly, In Praise of Erie — And of the New Federal Common Law, 39 N.Y. U. L. Rev. 383. 410 (1964). At least this first step of the Clearfield analysis is applicable here. We deal with the interpretation of a land acquisition agreement (a) explicitly authorized, though not precisely governed, by the Migratory Bird Conservation Act and (b) to which the United States itself is a party. Cf. Bank of America v. Parnell, 352 U.S. 29, 33 (1956). As in Clearfield and its progeny, "[t]he duties imposed upon the United States and the rights acquired by it . . . find their roots in the same federal sources. . . . In absence of an applicable Act of Congress it is for the federal courts to fashion the governing rule of law according to their own standards." 318 U.S., at 366-367; United States v. Allegheny County, 322 U.S. 174, 183 (1944); United States v. Standard Oil Co., 332 U.S. 301, 305 (1947); Board of County Comm'rs v. United States, 308 U.S. 343, 349-350 (1939).

III

The next step in our analysis is to determine whether the 1937 and 1939 land acquisition agreements in issue should be interpreted according to "borrowed" state law — Act 315 of 1940. The availability of this choice was explicitly recognized in Clearfield Trust itself and fully elaborated some years later in United States v. Standard Oil Co., supra. There we acknowledged that "in many situations, and apart from any supposed influence of the Erie decision, rights, interests and legal relations of the United States are determined by application of state law, where Congress has not acted specifically." 332 U.S., at 308. We went on to observe that whether state law is to be applied is a question "of federal policy, affecting not merely the federal judicial establishment and the groundings of its action, but also the Government's legal interests and relations, a factor not controlling in the types of cases producing and governed by the Erie ruling. And the answer to be given necessarily is dependent upon a variety of considerations always relevant to the nature of the specific governmental interests and to the effects upon them of applying state law." Id., at 309-310. See also De Sylva v. Ballentine, 351 U.S. 570, 580 (1956); RFC v. Beaver County, 328 U.S. 204 (1946); Board of County Comm'rs v. United States, 308 U.S., at 351-352; Royal Indemnity Co. v. United States, 313 U.S. 289, 296 (1941); United States v. Yazell, 382 U.S. 341, 356-357 (1966); cf. United States v. Mitchell, 403 U.S. 190 (1971).

The Government urges us to decide, virtually without qualification, that land acquisition agreements of the United States should be governed by federally created federal law. Cf. United States v. 93.970 Acres, 360 U.S. 328 (1959). We find it unnecessary to resolve this case on such broad terms. For even if it be assumed that the established body of state property law should generally govern federal land acquisitions, we are persuaded that the particular rule of law before us today — Louisiana's Act 315 of 1940, as retroactively applied — may not. The "reasons which may make state law at times the appropriate federal rule are singularly inappropriate here." Clearfield Trust, 318 U.S., at 367.

The Court in the past has been careful to state that, even assuming in general terms the appropriateness of "borrowing" state law, specific aberrant or hostile state rules do not provide appropriate standards for federal law. In De Sylva v. Ballentine, supra, we held that whether an illegitimate child was a "child" of the author entitled under the Copyright Act to renew the author's copyright was to be determined by whether, under state law, the child would be an heir of the author. But Mr. Justice Harlan's opinion for the Court took pains to caution that the Court's holding "does not mean that a State would be entitled to use the word 'children' in a way entirely strange to those familiar with its ordinary usage . . . ." 351 U.S., at 581. In RFC v. Beaver County, supra, the issue was whether the definition of "real property," owned by the RFC and authorized by Congress to be subject to state and local taxation, was to be derived from state law or to be fashioned as an independent body of federal law. The Court concluded that "the congressional purpose can best be accomplished by application of settled state rules as to what constitutes 'real property'" — but again the Court foresaw that its approach would be acceptable only "so long as it is plain, as it is here, that the state rules do not effect a discrimination against the Government, or patently run counter to the terms of the Act." 328 U.S., at 210. See also U.A.W. v. Hoosier Cardinal Corp., 383 U.S. 696, 706 (1966).

Under Louisiana's Act 315, land acquisitions of the United States, explicitly authorized by the Migratory Bird Conservation Act, are made subject to a rule of retroactive imprescriptibility, a rule that is plainly hostile to the interests of the United States. As applied to a consummated land transaction under a contract which specifically defined conditions for prolonging the vendor's mineral reservation, retroactive application of Act 315 to the United States deprives it of bargained-for contractual interests.

To permit state abrogation of the explicit terms of a federal land acquisition would deal a serious blow to the congressional scheme contemplated by the Migratory Bird Conservation Act and indeed all other federal land acquisition programs. These programs are national in scope. They anticipate acute and active bargaining by officials of the United States charged with making the best possible use of limited federal conservation appropriations. Certainty and finality are indispensable in any land transaction, but they are especially critical when, as here, the federal officials carrying out the mandate of Congress irrevocably commit scarce funds.

The legislative history of the Migratory Bird Conservation Act confirms the importance of contractual certainty to the federal land acquisition program it authorizes. As originally enacted in 1929, the Act provided that land acquisitions might include reservations, easements, and rights of way but that these were to be subject to "such rules and regulations" as the Secretary of Agriculture might prescribe "from time to time." § 6, 45 Stat. 1223. This sweeping statement of the Secretary's power to modify contract terms in favor of the Government had an unsettling effect on potential vendors; in 1935, the Act was amended to require the Secretary either to include his rules or regulations in the contract itself or to state in the contract that the reservation or easement would be subject to rules and regulations promulgated "from time to time." A Congress solicitous of the interests of private vendors in the certainty of contract would hardly condone state modification of the contractual terms specified by the United States itself as vendee, whether or not those terms may be characterized as "rules and regulations" within the meaning of the Act.

Conceivably, our conclusion might be influenced if Louisiana's Act 315 of 1940, as applied retroactively, served legitimate and important state interests the fulfillment of which Congress might have contemplated through application of state law. But that is not the case. We do not deprecate Louisiana's concern with facilitating federal land acquisitions by removing uncertainty on the part of reluctant vendors over the duration of mineral reservations retained by them. From all appearances, this concern was a significant force behind the enactment of the 1940 legislation. But today we are not asked to consider Act 315 on its face, or as applied to transactions consummated after 1940; we are concerned with the application of Act 315 to a pair of acquisition agreements in 1937 and 1939. And however legitimate the State's interest in facilitating federal land acquisitions, that interest has no application to transactions already completed at the time of the enactment of Act 315: the legislature cannot "facilitate" transactions already consummated.

The Louisiana Supreme Court has candidly acknowledged two additional purposes which help to explain retroactive application of Act 315: to clarify the taxability by the State of mineral interests in the large federal land holdings in Louisiana, otherwise in doubt by virtue of the arcane and fluctuating doctrines of intergovernmental tax immunity; and to ensure that federal mineral interests could be subjected to state mineral conservation laws without federal pre-emption. We are not unsympathetic to Louisiana's concern for the consequences of a continuing, substantial, even if contingent, federal interest in Louisiana minerals. Congress, however, could scarcely have viewed that concern as a proper justification for retroactive application of state legislation which effectively deprives the Government of its bargained-for contractual interests. Our Federal Union is a complicated organism, but its legal processes cannot legitimately be simplified through the inviting expedient of special legislation which has the effect of confiscating interests of the United States.

Respondents point out that "[o]ne who owns land subject to an outstanding mineral reservation possesses no vested property interest [under Louisiana law], inasmuch as 'estates in reversion' are unknown to Louisiana law. Such an owner of the land possesses only a hope or expectancy to acquire these mineral rights; and . . . this hope or expectancy is not an object that can be legally sold." Brief for Respondents 27, citing, e.g., Hicks v. Clark, 225 La. 133, 72 So.2d 322 (1954). But whether Louisiana recognizes the interests at stake here as transferable interests in real property, as such, has no bearing on our conclusion that after-the-fact modification of explicit contractual terms would be adverse to the United States and contrary to the requirements of the Migratory Bird Conservation Act.

It is also of no import that, under Louisiana law as it might be articulated in 1973, the United States acquired from respondents only the reversion to a mineral interest of indefinite duration, a "hope" or "expectancy" revocable at any time by after-enacted legislation. Respondents place heavy reliance on the opinion of the Louisiana Supreme Court in Leiter Minerals, where that court held that a mineral reservation for an indefinite duration was one traditionally subject to retroactive prescriptive change. But even if this rule of law could have been anticipated in 1937 and 1939, when the United States agreed to the mineral reservations in issue here, that the 1937 and 1939 reservations were of "indefinite" duration could not have been. Indeed, some 20 years later, in 1957, when Leiter Minerals came to this Court for the first time, we were not in a position to resolve the Government's contention that the Leiter reservation was one of specific duration. Uncertainty over this question of Louisiana law was the guiding force behind our remand in hopes of obtaining the view of the Louisiana Supreme Court. In its advisory opinion, the Louisiana Supreme Court did not decide whether the Leiter-type reservation was "indefinite" and subject to retroactive modification — to the extent that the Federal District Court, in Louisiana, subsequently concluded that the servitude in the Leiter reservation was not, under state law, freely revocable. In Leiter Minerals, one Court of Appeals judge dissented on this state law issue, and, with reason, the Government renews the issue before the Court in this case.

Were the terms of the mineral reservations at issue here less detailed and specific, it might be said that the Government acknowledged and intended to be bound by unforeseeable changes in state law. But the mineral reservations before us are flatly inconsistent with the respondents' suggestion that the United States in fact expected that these reservations would be wholly subject to retroactive modification. Nor, given the absence of any reliable contemporaneous Louisiana signpost and the absence even today of any final resolution of the pertinent state law question, can we say that the United States ought to have anticipated that its deed contained an empty promise. Respondents' reliance on the Louisiana Supreme Court's holding in its opinion in 1961 in Leiter Minerals assumes that a late-crystallizing doctrine of state law is appropriately applied to modify the expectations of the United States established by the terms of 1937 and 1939 bargains. The argument, however, is indistinguishable from respondents' defense of Act 315 itself. Years after the fact, state law may not redefine federal contract terminology "in a way entirely strange to those familiar with its ordinary usage . . . ." De Sylva v. Ballentine, 351 U.S., at 581.

IV

In speaking of the choice of law to be applied, the alternatives are plain although in this case identifying them in fixed categories is somewhat elusive. One "choice" would be to apply the law urged on us by respondents, i. e., Louisiana Act 315 of 1940. In some circumstances, such as those suggested by RFC v. Beaver County, 328 U.S. 204 (1946), or Wallis v. Pan American Petroleum Corp., 384 U.S. 63 (1966), state law may be found an acceptable choice, possibly even when the United States itself is a contracting party. However, in a setting in which the rights of the United States are at issue in a contract to which it is a party and "the issue's outcome bears some relationship to a federal program, no rule may be applied which would not be wholly in accord with that program." Mishkin, 105 U. Pa. L. Rev., at 805-806.

Since Act 315 is plainly not in accord with the federal program implemented by the 1937 and 1939 land acquisitions, state law is not a permissible choice here. The choice of law merges with the constitutional demands of controlling federal legislation; we turn away from state law by default. Once it is clear that Act 315 has no application here, we need not choose between "borrowing" some residual state rule of interpretation or formulating an independent federal "common law" rule; neither rule is the law of Louisiana yet either rule resolves this dispute in the Government's favor. The contract itself is unequivocal; the District Court concluded, and it is not disputed here, that by the clear and explicit terms of the contract reservations, "[respondents'] interests in the oil, gas, sulphur and other minerals terminated . . . no later than July 23, 1947, and August 30, 1949, unless Act 315 of 1940 has caused the reservations of the servitudes in favor of [respondents] to be imprescriptible."

We hold that, under settled principles governing the choice of law by federal courts, Louisiana's Act 315 of 1940 has no application to the mineral reservations agreed to by the United States and respondents in 1937 and 1939, and that, as a result, any contract interests of respondents expired on the dates identified by the District Court. Accordingly, we reverse the judgment of the Court of Appeals and remand the case for entry of an order consistent with this opinion.

Reversed and remanded.