delivered the opinion of the Court.
This case presents a question concerning “federal common law" best explained after a summary of the facts and the legal proceedings involved.
At stake in the litigation are rights in several tracts, aggregating 827 acres, of oil-rich “mud lumps” or islands owned by the United States and located in a mouth of the Mississippi River near Burrwood, Louisiana. 1 In *65 1954 petitioner, Floyd Wallis, filed with the Secretary of the Interior applications for a lease to exploit oil and gas deposits in the tracts. Because the tracts were deemed by Wallis to be “acquired lands” of the United States rather than “public domain lands,” these applications were filed under the Mineral Leasing Act for Acquired Lands, which governs the former, instead of the Mineral Leasing Act of 1920, which controls the latter. 2 Subsequently, Wallis entered into a written joint venture agreement with respondent Patrick McKenna giving McKenna a one-third interest in the pending applications and any lease issued under those applications. Then Wallis, who had exclusive management of the property under his agreement with McKenna, sold respondent Pan American Petroleum Corporation an option to acquire any lease Wallis might obtain under the applications then on file with the Secretary.
In 1956, fearing that the tracts might prove to be public domain land, Wallis filed new applications for the same tracts under the Mineral Leasing Act of 1920.
3
Thereafter the tracts were ruled to be public domain land, the conflicting applications of one or more competitors were rejected, and in 1958 the Secretary issued a lease of the tracts to Wallis under the 1920 Act. See
Morgan
v.
Udall,
The actions were consolidated, and following a nonjury trial the District Court held that neither McKenna nor Pan American was entitled to any interest in the disputed lease.
Over a dissent, the Court of Appéals for the Fifth Circuit reversed, filing an initial opinion,
The question before us is whether in general federal or state law should govern the dealings of private parties in an oil and gas lease validly issued under the Mineral Leasing Act of 1920. 5 Several related matters in the case should be distinguished and laid aside at the outset.
First, we are not concerned with whether under
Erie R. Co.
v.
Tompkins,
We focus now on the central question in the case. In deciding whether rules of federal common law should be fashioned, normally the guiding principle is that a significant conflict between some federal policy or interest and the use of state law in the premises must first be specifically shown. It is by no means enough that, as we may assume, Congress could under the Constitution readily enact a complete code of law governing transactions in federal mineral leases among private parties. Whether latent federal power should be exercised to displace state law is primarily a decision for Congress. Even where there is related federal legislation in an area, as is true in this instance, it must be remembered that “Congress acts . . . against the background of the total
corpus juris
of the states . . . .” Hart
&
Wechsler, The Federal Courts and the Federal System 435 (1953). Because we find no significant threat to any identifiable federal policy or interest, we do not press on to consider other questions relevant to invoking federal common law, such as the strength of the state interest in having its own rules govern, cf.
United States
v.
Yazell,
If there is a federal statute dealing with the general subject, it is a prime repository of federal policy and a starting point for federal common law. See
Deitrick
v.
Greaney,
Perhaps most prominent among those that are relevant is § 30a, 30 U. S. C. § 187a, which provides that oil and gas leases shall be assignable.
6
The Court of Appeals’ opinion relied on this provision, together with reasons why assignment of leases may promote federal policy, in justifying the use of federal rather than state law. How
*70
ever fitting this approach may be where a State interposes unreasonable conditions on assignability, it can have no force in this instance because Louisiana concededly provides a quite feasible route for transferring any mineral lease or contracting to do so, namely, by written instrument. See
Nor is respondents’ position aided by the provisions fixing qualifications for lessees to the extent of curtailing alien ownership and limiting any lessee or option holder to a maximum number of acres. 7 The Secretary, who must approve all assignments before the lease obligations or record titles are shifted finally, is entirely free to disapprove assignees however valid their assignments may otherwise be. 8 Finally, it is said that because the leases are issued by the United States and concern *71 federal lands, there is a federal interest in having private disputes over them justly resolved. Apart from the highly abstract nature of this interest, there has been no showing that state law is not adequate to achieve it.
A concluding word must be said about precedents in this Court, which have been copiously cited in this litigation. The Court of Appeals in its initial opinion and at least one of the respondents in his brief have sought support in the general principle, repeated in a number of our cases, that the transfer of property by the United States to a private party is governed by federal law and only subsequent transfers among private parties are subject to state law.
E. g., Wilcox
v.
Jackson,
We take the decision in
Irvine
to rest on its most precise explanation: that enforcement of the equitable claim was required because the local rule discouraged purchasing through agents and so threatened to hamper the Federal Government in selling its land.
Having concluded that federal law should not govern the present controversy, we vacate the judgment of the Court of Appeals and remand the case to that court so that it may consider any other contentions respondents may have urged, including their claim that they should prevail under Louisiana law.
Vacated and remanded.
Notes
Louisiana is said to have challenged the title of the United States in another suit, see
McKenna
v.
Wallis,
The Mineral Leasing Act for Acquired Lands is 61 Stat. 913, 30 U. S. C. §§351-359 (1964 ed.); the Mineral Leasing Act of 1920 is 41 Stat. 437, as amended, 30 U. S. C. § 181 et seq. (1964 ed.). While the precise distinction is of no concern here, in general acquired lands are those granted or sold to the United States by a State or citizen and public domain lands were usually never in state or private ownership.
It appears that applications filed under the wrong Act are treated as ineffective,
See also other arguably conflicting decisions in the Fifth, Ninth, and Tenth Circuits collected in 40 Tulane L. Rev. 195, 199, nn. 18-20.
How possible federal rules would differ from those used by Louisiana has not been specified precisely. The Court of Appeals intimated that the devices of resulting and constructive trusts, said not to be recognized in Louisiana, might be available under federal law and useful to respondents. It may be thought that federal law would not embody a statute of frauds so oral understandings could be proved. In this instance, we believe the question of applicability of state versus federal law can be decided without further refinement of the issue.
Other provisions that have something to do with transfer of lease rights are ones providing for surrender of leases to the Secretary, §30, 30 U. S. C. §187; for a time period in which persons may dispose of leases illegally held but involuntarily acquired, § 27 (g), 30 U. S. C. § 184 (g); and for protecting the rights of bona fide purchasers if the Secretary seeks to cancel a lease for violations of the Act, §27 (h), 30 U. S. C. § 184 (h). Nowhere is it suggested how use of Louisiana law on the questions before us might interfere with policies behind these sections, whose provisions basically relate to the rights of private persons vis-á-vis the Secretary.
§§ 1, 27 (d), 30 U. S. C. §§ 181, 184 (d). Conceivably, the rights of private parties among themselves might be relevant data in deciding whether these sections were violated, e. g., whether an alien “controlled” a lease within the meaning of the statute; since the relevance would itself be decided by federal law, the federal interest is secure.
Section 30a, 30 U. S. C. § 187a, requires approval unless the assignee is not qualified or fails to post the required bond. Where there is a private dispute as to the validity or effect of an assignment, the Secretary does not decide the question and he will not approve the assignment or take other action until the parties settle their dispute in court. See McCulloch Oil Corp. of California, Int. Dept. Decision No. A-30208 (Nov. 25, 1964).
