This case involves the scope of state authority to tax the proceeds of tribal mineral leases, and requires that we examine a series of congressional enactments regulating the leasing of tribal land for oil and gas production.

Between 1932 and 1968, the Blackfeet Tribe executed 125 leases authorizing the mining of oil and gas on tribal land located within the Blackfeet Indian Reservation. Approximately 12 of the leases were made under the authority of the Act of February 28, 1891, ch. 383, 26 Stat. 795 , as amended by the Act of May 29, 1924, ch. 210, 43 Stat. 244 (codified at 25 U.S.C. §§ 397-98 (1976)). The balance of the leases were made under the authority of the Act of May 11, 1938, ch. 198, 52 Stat. 347 (codified at 25 U.S.C. §§ 396a-396g (1976)). All 125 leases remain in operation today and will continue until the oil and gas supply is exhausted. The Tribe is paid royalties calculated on the basis of the amount of gas or oil produced under the leases. The State of Montana imposes four distinct taxes on the Tribe’s royalty interests, without distinguishing between the royalties collected pursuant to 1938 Act leases and the royalties collected under 1891 Act leases. See Mont.Code Ann. §§ 15-36-101 to -121 (1981) (Oil and Gas Severance Tax); Mont.Code Ann. §§ 15-38-101 to -109 (1981) (Resource Indemnity Trust Tax); Mont.Code Ann. §§ 82-11-131 to -132 (1981) (Oil and Gas Conservation Tax); Mont.Code Ann. §§ 15-23-601 to -612 (1981) (Oil and Gas Net Proceeds Tax). Montana assesses the Tribe’s share of all four taxes against the producer-lessees, who then deduct it from the royalties payable to the Tribe.

In 1977, the Solicitor of the Department of the Interior issued an opinion concluding that Montana was entitled to tax the production of oil and gas under 1891 Act leas *1194 es, but could not tax tribal proceeds from 1938 Act leases. Tax Status of The Production of Oil and Gas from Leases of The Fort Peck Tribal Lands Under The 1938 Mineral Leasing Act, 84 Interior Dec. 905 (1977). 1 Montana continued to assess taxes against the Tribe’s royalty interests under all 125 leases. In 1978, the Tribe filed an action in federal court seeking to enjoin Montana’s taxation of tribal royalties. The district court, 507 F.Supp. 446 , entered summary judgment for the State of Montana, holding that the 1924 amendment to the 1891 Act expressly authorized state taxation of production of oil and gas on Indian lands, and that the 1938 Act left that authority undisturbed.

A panel of this court affirmed the district court’s decision. We ordered a rehearing en banc in order to resolve a conflict between the opinion and our decision in Crow Tribe of Indians v. State of Montana, 650 F.2d 1104 (9th Cir.1981), amended, 665 F.2d 1390 (9th Cir.), cert. denied, 459 U.S. 916 , 103 S.Ct. 230 , 74 L.Ed.2d 182 (1982).

Montana argues on appeal that Congress consented to the imposition of its taxes in the Act of May 29, 1924. The Tribe concedes that the 1924 Act expressly consented to taxation of oil and gas production on Indian land, but argues that the 1924 Act was implicitly repealed by section 7 of the Act of May 11, 1938. 2 Alternatively, the Tribe argues that the consent to taxation found in the 1924 Act is inapplicable to production of oil and gas under leases governed by the 1938 Act. The legislative history of the two statutes contains little explicit guidance, and resort to conventional “canons of construction” yields inconsistent results. 3 Our resolution of this difficult issue requires a thorough analysis of the language, purpose and historical contexts of both statutory schemes.

I

We begin with the well settled principle that state taxation of tribal income from activities carried on within the boundaries of the reservation is impermissible unless Congress has expressly consented to the imposition of the tax. See Bryan v. Itasca County, 426 U.S. 373 , 96 S.Ct. 2102 , 48 L.Ed.2d 710 (1976); Moe v. Confederated Salish & Kootenai Tribes, 425 U.S. 463, 96 S.Ct. 1634 , 48 L.Ed.2d 96 (1976). We must resolve whether the 1924 Act explicitly consented to the taxes here at issue. The consent to taxation contained in the 1924 Act was part of an amendment to the Act of February 28, 1891, ch. 383, 26 Stat. 794 , which was itself an amendment to the General Allotment Act of February 8,1887, ch. 119, 24 Stat. 388 . The 1924 Act was one of a series of similar statutes providing for non-Indian leasing and development of Indian lands within the context of the policies embodied in the General Allotment Act. See, e.g., Appropriations Act of June 30, 1919, ch. 4, § 26, 41 Stat. 3 , 31-34 (codified as amended at 25 U.S.C. § 399 (1976)); Act of September 20, 1922, ch. 347, 42 Stat. 857 (codified at 25 U.S.C. § 400 (1976)). 4 Our analysis therefore begins *1195 with the program reflected in the General Allotment Act of 1887, and Congress’s efforts to effectuate it.

The primary purpose of the General Allotment Act was the speedy assimilation of the Indians. See generally 17 Cong.Rec. 1630-35, 1762-64 (1886); F. Cohen, Handbook of Federal Indian Law 128-32 (1982). Each Indian was to receive an allotment of land, to be held in trust for 25 years. 5 The Forty-Ninth Congress envisioned a period during which the Indians would be “civilized” and the tribal system destroyed, after which the Indians would succeed to fee ownership of their lands and all of the privileges and obligations of citizenship. See, e.g., 17 Cong.Rec. 1632 (1886) (remarks of Mr. Maxey); id. at 1763 (remarks of Mr. Dawes); F. Cohen, supra, at 131-32; G.D. Taylor, The New Deal and American Indian Tribalism 4-5 (1980). The Act further provided for the sale of surplus land, and the use of the proceeds for the education and civilization of members of the tribes. 6

In 1891, Congress responded to public pressure to open reservation land for settlement and mining by amending the allotment act to permit short term leases of unallotted lands and lands allotted to aged and disabled allottees. See Act of February 28, 1891, ch. 383, § 3, 26 Stat. 794 , 795; F. Cohen, supra, at 134-35. 7 In 1910, Congress enacted a measure permitting short term leasing of allotted lands and directing the Secretary of the Interior to supervise the expenditure of funds earned under the leases. 8 See Act of June 25, 1910, ch. 431, § 4, 36 Stat. 855 , 856. The Indian Appropriations Act of 1919 included comprehensive provisions permitting long term mineral leasing of unallotted lands in western states. See Appropriations Act of June 30, 1919, ch. 4, § 26, 41 Stat. 3 , 31-34 (codified as amended at 25 U.S.C. § 399 (1976)). The Act of May 29, 1924, ch. 210, 43 Stat. 244 , extended the terms of 1891 Act oil and gas production leases from a ten-year period to “as long as oil or gas shall be found in paying quantities,” authorized the Secretary of the Interior to enter into further oil and gas leases for the extended period, and consented to state taxation of mineral production on unallotted lands “bought and paid for” by the Indians. See British-American Oil Producing Co. v. Board of Equalization, 299 U.S. 159 , 57 S.Ct. 132 , 81 L.Ed. 95 (1936). 9 Between 1920 and *1196 1930, several other statutes were enacted to permit the leasing of additional categories of reservation land. 10

All of these leasing provisions had a number of common features. The leases were regulated and approved by the Secretary of the Interior. 11 The proceeds were paid to the Secretary of the Interior and disbursed, by congressional appropriation, for the benefit of the Indians. The tribes had no authority to police or cancel leases or to direct the purposes for which revenue earned under the leases would be spent. See generally F. Cohen, supra, at 533-34.

The legislative history of these enactments reflects certain common themes. Congress evinced concern about the increasing size of Indian appropriations, and desired that a greater portion of the federal expenditures be made from the Indians’ funds. See, e.g., H.Rep. No. 1791, 69th Cong.2d Sess. (1927); 68 Cong.Rec. 4574-75 (1927) (remarks of Mr. Letts); 58 Cong.Rec. 175 (1919) (remarks of Mr. Snyder); id. at 207-08 (colloquy); F. Cohen, supra, at 135-36. Representatives expressed frustration at the fact that the assimilation sought under the General Allotment Act failed to proceed with the contemplated dispatch. See, e.g., 68 Cong.Rec. 4704 (1927) (remarks of Mr. Morrow); 58 Cong.Rec. 174-75 (1919) (remarks of Mr. Snyder). States complained that reservation lands were remaining tax exempt for too long a period, see 58 Cong.Rec. 180-81 (1919) (remarks of Mr. McKeown); id. at 184 (remarks of Mr. Howard); 45 Cong.Rec. 6079 (1910) (colloquy), and urged strenuously that the lands be opened for increased non-Indian development and settlement. See, e.g., 68 Cong.Rec. 4575 (1927) (remarks of Mr. Frear); 58 Cong.Rec. 181 (1919) (remarks of Mr. McKeown); id. at 216 (remarks of Mr. Carter); 45 Cong.Rec. 6096 (1910) (remarks of Mr. McGuire); F. Cohen, supra, at 128, 134-35.

The 1924 Act was responsive to these concerns. By extending the period of oil and gas production leases it encouraged further non-Indian development of reservation lands. The revenue thereby produced became available to reimburse the Treasury for its appropriations for the Indians’ “education” and “civilization” — measures that Congress hoped would speed assimilation. 12 The consent to taxation placated states impatient with the Indians’ tax-exempt status. 13 See S.Rep. No. 546, 68th Cong., 1st Sess. (1924); 65 Cong.Rec. 6844 (1924) (Remarks of Mr. Hastings); see generally F. Cohen, supra, at 134-42, 533-34; United States Department of the Interior, Federal Indian Law 125-26 (1958).

In 1934, Congress repudiated the allotment program. After studying its ma *1197 plementation, members of the Congressional Committees on Indian Affairs concluded that the results of the program had become “a scandal and a blot on our name in every part of the world.” 78 Cong.Rec. 11727 (1934) (remarks of Mr. Howard). See also id. at 11126 (remarks of Mr. King); id. at 11743 (remarks of Mr. Frear). 14 In a complete about-face, Congress enacted legislation to reverse the effects of 47 years of federal Indian policy. The Indian Reorganization Act [IRA], ch. 576, 48 Stat. 984 (1934) (codified as amended at 25 U.S.C. §§ 461-479 (1976)), prohibited further allotment of Indian land, sought to return to the Tribes some portion of the 90 million acres of Indian land that had passed into non-Indian ownership under the allotment program, and authorized tribes to establish tribal governments with authority over the development and exploitation of Indian land and resources. Tribes that elected to organize under the Act were entitled “to prevent the sale, disposition, lease or encumbrance of tribal lands, interests in lands, or other tribal assets without the consent of the tribe____” IRA § 16, 48 Stat. 984 , 987 (codified at 25 U.S.C. § 476 (1976)). Among the purposes of the IRA were the promotion of a significant increase in tribal autonomy and authority and the extension to the tribes of “an opportunity to take over the control of their own resources.” 78 Cong.Rec. 11123-25 (1934) (remarks of Mr. Wheeler). See Morton v. Mancari, 417 U.S. 535, 542 , 94 S.Ct. 2474, 2478 , 41 L.Ed.2d 290 (1974); F. Cohen, supra, at 147. The tax exempt and trust status of unalloted and restricted reservation lands was continued indefinitely, a provision that induced at least one state to insist that tribes within its borders be excluded from the Act. See 78 Cong.Rec. *1198 11126 (1934) (remarks of Mr. Thomas); IRA § 13 (codified at 25 U.S.C. § 473 (1976)). 15

Congress recognized that the various statutory provisions permitting leasing of tribal land were scattered, inconsistent, and in conflict with the provisions of the IRA giving the tribes authority to prevent leasing of tribal lands. In 1935 Congress considered, but did not enact, a bill intended to amend existing leasing statutes to permit tribal councils to grant leases for the mining of unallotted lands, subject to the approval and regulations of the Secretary of the Interior. 16 Ultimately, Congress decided to replace, rather than amend, existing leasing laws. In 1937, after extensive hearings on the conditions under which Indians were living, 17 the Senate and House Committees on Indian Affairs introduced bills to “bring all mineral-leasing matters in harmony with the Indian Reorganization Act.” See S.Rep. No. 985, 75th Cong., 1st Sess. 3 (1937); H.R.Rep. No. 1872, 75th Cong., 3d Sess. (1938). The Senate Bill was enacted as the Act of May 11, 1938. 18 It *1199 replaced the prior mineral leasing statutes with a comprehensive and detailed procedure for mineral leasing of unallotted lands. See F. Cohen, supra, at 534. The Senate Report accompanying the bill noted that its purposes were to obtain uniformity with respect to the leasing of tribal lands, give Indians authority in granting or denying leases, and enable the Indians to gain the greatest return from their property. S.Rep. No. 985, 75th Cong., 1st Sess. 2 (1937). The Act made no mention of taxation, and the legislative history is silent on the issue.

*1200 II

The Tribe argues that the 1938 Act’s general repealer clause implicitly repealed the 1924 consent to taxation. We disagree. Many of the leases entered into under the authority of earlier statutes remained effective, indeed, remain effective today, because the prior statutory provisions authorized leases to continue for an indefinite term. See Appropriations Act of June 30, 1919, ch. 4, § 26, 41 Stat. 3 , 32 (“irrevocable” with certain exceptions); Act of May 29, 1924, ch. 210, 43 Stat. 244 (“as long as oil or gas shall be found in paying quantities”). The 1938 Act expressly limits its application to leases entered into after the Act’s effective date. In section one, the Act provides that “hereafter unallotted lands ... may ... be leased for mining purposes____” The “hereafter” language is echoed in section 3 of the Act. Finally, section 4 of the Act provides that “operations under any oil, gas, or other mineral lease issued pursuant to the terms of this or any other Act affecting restricted Indian lands shall be subject to the rules and regulations promulgated by the Secretary of the Interior.” (Emphasis supplied). We infer from the statutory language that Congress envisioned that leases issued pursuant to prior acts would continue to be effective for their duration, subject to regulations promulgated by the Secretary and to the statutes under which they were executed. Leases made after the effective date of the Act, however, were to be governed by the new terms and procedures. 19 This interpretation, we believe, is both the most natural reading of the statutory language and the reading best adapted to the effectuation of the statute’s purposes. To infer repeal of the prior statutes on the basis of the general repealer in section 7 of the Act would introduce serious uncertainty as to the legal'status of the indefinite-term leases executed under earlier acts and cast doubt on the Secretary’s authority to continue to regulate them. Such a result would serve neither the interests of the Tribe nor the interests of the producer-lessees.

Having concluded that the 1938 Act superseded but did not repeal prior leasing statutes, we turn to the current effect of the consent to taxation contained in the 1924 amendment to the 1891 Act. We hold that leases executed pursuant to the 1891 and 1924 Acts remain subject to those Acts, and to the regulations promulgated by the Secretary under the authority of section 4 of the 1938 Act for regulation of leases issued “pursuant to the terms of this or any other Act.” It follows that the 1924 Act’s consent to state taxation remains effective with respect to leases executed under the 1924 and 1891 Acts. 20 We therefore affirm the district court’s grant of summary judgment to the State of Montana insofar as it upholds the validity of taxing tribal proceeds from 1924 Act and 1891 Act leases.

Ill

Montana argues that if the 1938 Act did not implicitly repeal the 1924 Act, it must be read implicitly to have incorporated the 1924 Act. Therefore, Montana contends, if it may tax oil and gas production under 1891 and 1924 Act leases, it may tax production under 1938 Act leases as well. The *1201 district court found this argument persuasive. We do not.

The 1924 Act in its entirety provides as follows:

Ch. 211, 43 Stat. 244 (codified at 25 U.S.C. § 398 (1976)). Montana concedes that the provisions of the Act concerned with the procedure for issuing leases and the duration of leases have been superseded by the 1938 Act. Moreover, the statutory method for collecting the tax — disbursement by the Secretary — seems equally inapplicable to the current leases. Montana argues, however, that the language “Provided, that the production of oil or gas and other minerals on such lands may be taxed by the State in which said lands are located in all respects the same as production on unrestricted lands ...” is nowhere contradicted by the 1938 Act and is inconsistent with no provision of the later statute. Therefore, Montana insists, Congress’s silence in 1938 on the subject of taxation must be interpreted as an implicit incorporation of the taxation portion of the 1924 Act into the 1938 statutory scheme.

Montana’s argument is, in essence, an invocation of assorted maxims of statutory construction. Citing United States v. Greathouse, 166 U.S. 601, 605 , 17 S.Ct. 701, 703 , 41 L.Ed. 1130 (1897), Montana advises us of the rule that where two statutes on the same subject matter are not absolutely irreconcilable, both should be given effect. Montana also draws comfort from the canon that a long held agency interpretation of a statute in which Congress has silently acquiesced is entitled to great deference. See United States v. Rutherford, 442 U.S. 544, 554 , 99 S.Ct. 2470, 2476 , 61 L.Ed.2d 68 (1979). Montana points to informal decisions by the Solicitor of the Interior Department in 1956 and 1966 concluding that the 1924-Act’s consent to state taxation applied to 1938 Act leases, and notes that the Department did not overrule these opinions until 1977. See 84 Interior Dec. 905 , 911 (1977). In view of Congress’s failure to alter the Department’s 1956 interpretation, Montana suggests that the Department behaved improperly in repudiating its earlier view. Therefore, it concludes, this court must defer to the Department’s 1956 position.

In invoking what it terms “the applicable rules of statutory construction,” by which, it insists, we are bound, Montana fails to appreciate that such rules are merely guideposts in discerning Congressional intent. See Busic v. United States, 446 U.S. 398, 406-07 , 100 S.Ct. 1747, 1752-53 , 64 L.Ed.2d 381 (1980); United States v. United Continental Tuna Corp., 425 U.S. 164, 168-69 , 96 S.Ct. 1319, 1322-23 , 47 L.Ed.2d 653 (1976); Gooch v. United States, 297 U.S. 124, 128 , 56 S.Ct. 395, 397 , 80 L.Ed. 522 (1936); Shields v. United *1202 States, 698 F.2d 987, 990 (9th Cir.), cert. denied, — U.S. -, 104 S.Ct. 73 , 78 L.Ed.2d 86 (1983).

Montana’s argument that the 1924 consent must be construed as a blanket consent to taxation, effective with respect to all mineral leases on unallotted treaty reservation lands unless issued under a statute prohibiting taxation, stretches the canon of construction disfavoring repeals by implication beyond its intended scope. The cases Montana cites that invoke this canon are not apposite. In one case, the canon was invoked to dispose of arguments that a statute addressing one concern repealed an earlier statute addressing another, see Morton v. Mancari, 417 U.S. 535 , 94 S.Ct. 2474 , 41 L.Ed.2d 290 (1974) (Civil Rights Act did not repeal portion of IRA); in another, to dispose of arguments that an amendment to one part of a statute repealed another part, see Posadas v. National City Bank, 296 U.S. 497 , 56 S.Ct. 349 , 80 L.Ed. 351 (1936) (amendment to § 25 of Federal Reserve Act did not repeal unamended portion of section). We do not quarrel with the proposition that it is generally unwise to conclude, in the absence of any evidence, that Congress intended to cause a prior statute to have no future effect. Where Congress has enacted legislation without attention to the provisions of prior Acts, courts should not attribute to Congress the unexpressed purpose of nullifying earlier statutes. This general principle, however, is inapplicable where, as here, all parties concede that Congress intended the later statute to supersede the prior one. In enacting the 1938 Act, Congress manifested an unmistakable intention to subject subsequent leases to the terms of the new statute rather than to its predecessors. The crucial inquiry is whether Congress nonetheless intended that a portion of one of the predecessor statutes control a lease issued under the 1938 Act.

In ascertaining Congress’s intent, we look to the language, legislative history and context of the 1938 Act, and find no manifestation of a purpose to subject leases under the new statutory scheme to the taxes authorized under several of the old statutory schemes. Montana asks that we infer such a purpose from Congress’s silence. The Supreme Court has instructed us, however, that congressional consent to state taxation of tribal income from on-reservation activities must be express. See Bryan v. Itasca County, 426 U.S. 373, 393 , 96 S.Ct. 2102, 2113 , 48 L.Ed.2d 710 (1976). We decline to hold that a canon of construction will suffice to supply the deficient express manifestation of Congress’s intent to permit the tax. 21

Montana also insists that we must interpret the two statutes in accordance with the Interior Department’s earlier position. The deference we should accord to administrative interpretations of statutes is not absolute. See Cruz v. Zapata Ocean Resources, Inc., 695 F.2d 428 (9th Cir.1982). In this case, we note several factors that undermine the authority of the 1956 interpretation. The Interior Department adopted its 1956 position informally, and without any analysis of the question before us — whether Congress intended the 1924 consent to taxation to apply to leases issued under the 1938 Act. See United States Dept. of the Interior Solicitor’s Opinion M-36345 (May 4, 1956) (unpublished). The Interior Department’s first articulation of this interpretation was not contemporaneous with the enactment of the 1938 statute, but rather, occurred 12 years later. The Department expressed this interpretation only in unpublished memoranda. The inference of Congressional acquiescence Montana would have us draw is undermined where, as here, there is no evidence that the Department’s interpretation was brought to Congress’s attention. See also Girouard v. United States, 328 U.S. 61, 69 , 66 S.Ct. 826, 829 , 90 L.Ed. 1084 (1946) (“It is at best treacherous to find in Congressional silence alone the adoption of a con *1203 trolling rale of law.”). Finally, the Department repudiated its earlier interpretation in 1977, see 84 Interior Dec. 905 (1977), in a published and carefully reasoned opinion that analyzed both statutes and the Department’s prior rulings. In 1979, the Department reexamined and adhered to its 1977 position. See 86 Interior Dec. 181 (1979). Under these circumstances, confronted with two non-eontemporaneous interpretations of the 1938 Act, we do not believe that we should defer to the informal, unpublished one merely because it is of earlier vintage.

We conclude that Montana’s collection of maxims is insufficient support for what we view to be an unlikely proposition: that Congress intended that part of one sentence in one of the statutes otherwise totally superseded by the 1938 Act be incorporated into the 1938 Act, and that Congress manifested its intention through silence. There is nothing in the legislative history or the language of the 1938 Act even hinting that Congress anticipated that the provisions of any of the prior leasing statutes would be applied to leases issued under the 1938 Act.

We note, in addition, that the 1924 Act was an integral part of Congress’s allotment program, under which all Indian land was intended to become subject to state taxation after the expiration of a brief trust period. See United States Department of the Interior, supra, at 856-59; supra section I. Congress’s consent to the exercise of state taxing authority over Indian Tribes was in harmony with the purposes of allotment. The 1938 Act, however, replaced prior mineral leasing statutes with a scheme calculated to advance the policies of tribal sovereignty and economic growth reflected in the IRA. We fail to see how interpreting the 1938 Act to incorporate implicitly the portion of the 1924 Act consenting to state taxation would advance purposes of the 1938 Act. 22

We hold that the 1924 Act’s consent to taxation is inapplicable to the 1938 Act and to leases executed pursuant to its authority. Accordingly, we reverse so much of the district court’s judgment as upheld the taxation of tribal royalties earned on 1938 Act leases.

IV

Montana argued to the district court that even if Congress had not consented to taxation of tribal proceeds from 1938 Act leases, its taxes were nonetheless valid because the legal incidence of the taxes fell on the non-Indian producer-lessees and not on the tribe. Because the district court concluded that the taxes were valid, it did not reach the question of the taxes’ legal incidence. We therefore remand the case to enable the district court to address this issue. Should the court determine that the legal incidence of the tax falls on the producer-lessees, it should then decide whether Montana’s statutes are preempted under the standards articulated in Crow Tribe of Indians v. State of Montana, 650 F.2d 1104 (9th Cir.1981), amended, 665 F.2d 1390 (9th Cir.), cert. denied, 459 U.S. 916 , 103 S.Ct. 230 , 74 L.Ed.2d 182 (1982).

*1204 AFFIRMED in part, REVERSED in part and REMANDED.

. Montana insists that no deference is due the interpretation of the Interior Department because its position in the six years since 1977 contradicts its position during the prior fifty years. Montana greatly overstates its case. Only two unpublished opinions, one in 1956 and a second in 1966, contradict the Department's current interpretation. See infra Section III. The other decisions on which Montana relies were either decided prior to the enactment of the 1938 leasing statute or concerned the taxation of leases issued under prior statutes. See 84 Interior Dec. at 911.

. Section 7 provides: "All Act or parts of Acts inconsistent herewith are hereby repealed.”

. The Tribe calls our attention to the canon that Indian legislation is to be construed liberally in favor of Indians and ambiguities to be resolved in their favor. Montana invokes the rule that repeals by implication are disfavored, insisting that courts must construe potentially inconsistent statutes so as to give both statutes effect.

. See also Appropriations Act of March 3, 1909, ch. 263, 35 Stat. 781 , 783 (codified at 25 U.S.C. § 396 (1976)); Act of April 28, 1924, ch. 135, 43 Stat. 111 (codified at 25 U.S.C. § 401 (1976)); Act of April 17, 1926, ch. 156, 44 Stat. 300 (codified at 25 U.S.C. § 400a (1976)); Act of March 3, 1927, ch. 299, 44 Stat. 1347 (codified at 25 U.S.C. § 398a (1976). See generally United States Department of the Interior, Federal Indi *1195 an Law 115-127 (1958); F. Cohen, Handbook of Federal Indian Law 132-43, 528-29 (1982).

. The trust period was subject to extension by the President, and was subsequently extended. See Appropriations Act of June 21, 1906, ch. 3504, 34 Stat. 325 , 326 (codified at 25 U.S.C. § 391 (1976)).

. See F. Cohen, supra note 4, at 131-32. During the first ten years of allotment, 55 million acres of "surplus” land were sold to white settlers. See G.D. Taylor, The New Deal and American Indian Tribalism 5 (1980). See also 78 Cong.Rec. 11134-37 (1934) (debate on effect of S. 3645, 73d Cong., 2d Sess., on surplus lands provision of 1887 Act).

. Minor relaxations in the restrictions on such leases were enacted over the next 20 years. See Appropriations Act of Aug. 15, 1894, ch. 290, 28 Stat. 286 , 305; Appropriations Act of May 31, 1900, ch. 598, § 1, 31 Stat. 221 , 229 (codified at 25 U.S.C. § 395 (1976)). See generally F. Cohen, supra note 4, at 135.

. See G.D. Taylor, supra note 6, at 6:

. In British-American Oil Producing Co. v. Board of Equalization, 299 U.S. 159, 164-65 , 57 S.Ct. 132, 134-35 , 81 L.Ed. 95 (1936), the Supreme Court construed the "bought and paid for" language to apply to unallotted land within treaty reservations, including unallotted reserved mineral rights in or under allotted lands. The Court held that the 1924 Act’s consent to taxation extended to mineral leases issued under the Appropriations Act of June 30, 1919, ch. 4, § 26, 41 Stat. 3 , 32 (codified as amended at 25 U.S.C. § 399 (1976)). Id. at 166, 57 S.Ct. at 135 . We believe that the British-American Court’s interpretation of the statutory language of the 1924 Act is problematic. See F. Cohen, supra note 4, at 409 n. 40, 529 n. 5. We follow it with respect to leases issued before the enactment of the 1938 statute. In view of our interpretation of *1196 the 1938 Act, we need not reach the question of whether the Court’s 1936 analysis applies to the 1938 Act. See id. at 529 n. 5.

. See Act of March 3, 1921, ch. 119, 41 Stat. 1225 , 1249 (Quapaw Reservation); Act of March 3, 1921, ch. 120, 41 Stat. 1249 , 1250 (Osage Reservation); Act of Sept. 20, 1922, ch. 347, 42 Stat. 857 (codified at 25 U.S.C. § 400 (1976)) (unallotted lands in Fort Peck and Blackfeet Reservations); Act of April 28, 1924, ch. 135, 43 Stat. 111 (codified at 25 U.S.C. § 401 (1976)) (unallotted lands in Kaw Reservation); Act of May 26, 1926, ch. 403, § 6, 44 Stat. 658 , 659-60 (Crow Reservation); Act of July 3, 1926, ch. 787, 44 Stat. 894 (codified at 25 U.S.C. § 402a (1976)) (unallotted irrigable lands for farming purposes); Act of March 3, 1927, ch. 299, 44 Stat. 1347 (codified at 25 U.S.C. 398a-398e (1976)) (unallotted lands on executive order reservations). The 1927 Act and both 1921 Acts expressly consented to state taxation; the other four Acts did not.

. Leases entered into under the 1891 Act were to be granted "by authority of the council speaking for such Indians ... subject to the approval of the Secretary of the Interior.” Act of Feb. 28, 1891, ch. 383, § 3, 26 Stat. 794 , 795. The 1924 Act amended the procedure to provide for leasing at public auction "by the Secretary of the Interior with the consent of the council speaking for such Indians.” Act of May 29, 1924, ch. 210, 43 Stat. 244 . The 1919 Act made no provision for tribal consent.

. See generally 58 Cong.Rec. 173-77 (1919); F. Cohen, supra note 4, at 139-41.

. See generally Loss of Revenue — Tax Exempt Indian Lands: Hearing on S.Res. 168 before the Senate Comm. on Indian Affairs, 75th Cong., 3d Sess. (1938), for accounts of unsuccessful state attempts to tax oil and mineral production on reservation lands during the early part of the twentieth century.

. Congressman Howard, a sponsor of the Indian Reorganization Act, described the allotment program as follows:

78 Cong.Rec. 11727-29 (1934).

. The district court noted that another purpose of the IRA was to enable Indians to enter the economic world on an equal footing. See, e.g., 78 Cong.Rec. 11730-31 (1934) (remarks of Mr. Howard). The IRA sought to accomplish this goal by authorizing tribes to form corporations, establishing a revolving credit fund for the benefit of these tribal corporations and their members, authorizing the purchase of additional land destined for tax-exempt Indian ownership, extending the tax-exempt and restricted status of existing unallotted Indian holdings, appropriating funds for college and technical education, and increasing Indian participation in and management of livestock and timber operations on tribal land. Id.; see also id. at 11123 (remarks of Mr. Wheeler).

Congress intended to effectuate increased tribal independence and economic power, but did not envision giving up federal responsibility for supervising these developments and providing necessary services for the Indians, and did not intend to turn its responsibility over to the states. Indeed, much of the opposition to the legislation was premised on its failure to reject protectionist policies. See, e.g., id. at 11126-27 (remarks of Mr. King); id. at 11733 (remarks of Mr. Kelley).

In the same legislative session, Congress enacted the Johnson-O'Malley Act, 48 Stat. 596 (codified as amended at 25 U.S.C. §§ 452-54 (1976)), authorizing the Secretary of the Interior to contract with state governments for the provision of education, health care, agricultural assistance and social services to Indians at federal expense. The legislative history of the Johnson-O’Malley Act indicates that Congress envisioned the federal government’s paying states to provide these benefits to Indians living in widely scattered communities where maintenance of separate federal services and facilities would be impractical. See S.Rep. No. 511, 73d Cong.2d Sess. (1934). A letter from Bureau of Indian Affairs Commissioner Collier, incorporated in the Senate Report, discloses that the Bureau anticipated that it would continue to provide services directly to Indians living in large tribal communities, unless the Indians themselves sought to take advantage of the possibility of state contract services. See id. at 4. Indeed, the Appropriations Act of March 2, 1934, ch. 38, 48 Stat. 362 , 366-79, had allocated several million dollars in federal and tribal funds for Indian education, and three million dollars for Indian health services, see 48 Stat. at 3771-76; see also 78 Cong.Rec. 821-22 (remarks of Mr. Howard).

The Appropriations Acts for the period following the enactment of the IRA demonstrate Congress’s continuing commitment to the principle that education, health care, social services and tribal police, firefighters and courts should be provided through a combination of federal and tribal funds. See, e.g., Appropriations Act of August 9, 1937, ch. 570, 50 Stat. 564 , 574-90; see also, e.g., 81 Cong.Rec. 4515-16 (1937) (remarks of Mr. Johnson); id. at 4589-90 (remarks of Mr. Burdick). We conclude, from our examination of the IRA and the statutes Congress enacted during the same period, that Congress did intend the IRA to assist Indians in achieving some measure of economic parity. It is manifest, however, that Congress did not intend for Indians to be dependent upon state governments for the benefits and services state governments traditionally provide.

. S. 2638, 74th Cong., 1st Sess. (1935). See 79 Cong.Rec. 6102, 7350, 7815, 8307, 8308, 8481 (1935).

. See, e.g., Survey of Conditions of the Indians in the United States: Hearings before a Subcomm. of the Senate Comm. on Indian Affairs, 75th Cong., 1st Sess. (1937); Survey of Conditions of the Indians in the United States: Hearings before a Subcomm. of the Senate Comm. on Indian Affairs, 74th Cong., 2d Sess. (1936); Conditions of Indians in the United States: Hearings before the House Comm. on Indian Affairs, 74th Cong., 2d Sess. (1936); Indian Conditions and Affairs: Hearings before the Subcomm. on General Bills of the House Comm. on Indian Affairs, 74th Cong., 1st Sess. (1935).

. The 1938 Act provided:

Act of May 11, 1938, ch. 198, 52 Stat. 347 (codified at 25 U.S.C. §§ 396a-396g (1976)).

Six reservations were excluded from the operation of much of the Act. These included the Papago Reservation, subject to special mineral leasing provisions of section 3 of the IRA, and the Crow Reservation, which voted against organizing under the IRA, see G.D. Taylor, supra note 6, at 33, and which was subject to leasing under the provisions of the Act of May 26, 1926, ch. 403, § 6, 44 Stat. 658 , 659. Also excluded were lands that the Shoshone Reservation had ceded to the United States, and three Oklahoma reservations that had been excluded from the IRA. The Crow and Papago reservations were ultimately made subject to the 1938 Act’s provisions. See Act of May 27, 1955, ch. 106, § 1, 69 Stat. 67 ; Act of May 17, 1968, Pub.L. 90-308, 82 Stat. 123. See generally P. Maxfield, M. Dieterich & F. Trelease, Natural Resources Law on American Indian Lands 164 (1977).

. We acknowledge that the statutory language is susceptible to more than one interpretation. The 1938 Act excludes six Indian tribes from its scope and, in addition, expressly preserves the authority of tribes organized under the IRA to lease lands for mining purposes according to the provisions of their tribal constitutions or charters. See supra note 18. The reference to leases issued pursuant to "any other statute" might thus be read to refer only to the IRA and statutes affecting the six excluded tribes. We feel constrained to reject this interpretation because it makes no provision for extant, indefinite-term leases entered into under prior statutes.

. Professor Cohen’s treatise suggests a similar interpretation:

F. Cohen, supra note 4, at 409 (emphasis supplied; footnotes omitted).

. We note in addition that commentators have expressed their opinions that the 1924 Act’s consent to taxation is inapplicable to 1938 Act leases. See, e.g., F. Cohen, supra note 4, at 409; see also M. Price and R. Clinton, Law and the American Indian 804 (1983).

. The district court found harmony between the purposes of the IRA and the 1924 consent to taxation on the theory that the IRA sought to enable Indians to enter the economic world on an equal footing and taxation statutes are economic facts of oil and gas production. In identifying this harmonious aspect, the district court disregarded the IRA’s express extension of the tax-exempt status of Indian land, see IRA §§ 2, 5; 48 Stat. 984 , 984, 985 (codified at 25 U.S.C. §§ 462 , 465 (1976)). In 1936, Congress acted to extend the tax exemption to land purchased with Indian trust or restricted funds, and appropriated money to reimburse Indians whose land had been taxed and redeem any land that had been forfeited for failure to pay assessed taxes. Act of June 20, 1936, ch. 622, 49 Stat. 984 (codified as amended at 25 U.S.C. § 412a (1976)). See H.R.Rep. 2398, 74th Cong., 2d Sess. (1936). Congress’s commitment to the tax exempt status of restricted land, and its continuing appropriations for Indian education, health care, tribal police and tribal courts, services traditionally provided to state citizens by state governments from state taxes, demonstrate to us that Congress did not intend for Indians to be treated equally for tax purposes. See, e.g., Appropriations Act of August 9, 1937, ch. 570, 50 Stat. 564 , 574-90.