JUSTICE O'CONNOR delivered the opinion of the Court. This case presents the question whether, in an 1894 statute that ratified an agreement for the sale of surplus tribal lands, Congress diminished the boundaries of the Yankton Sioux Reservation in South Dakota. The reservation was established pursuant to an 1858 Treaty between the United States and the Yankton Sioux Tribe. Subsequently, under the Indian General Allotment Act, Act of Feb. 8, 1887, 24 Stat. 388, 25 U. S. C. § 331 (Dawes Act), individual members of the Tribe received allotments of reservation land, and the Government then negotiated with the Tribe for the cession of the remaining, unallotted lands. The issue we confront illustrates the jurisdictional quandaries wrought by the allotment policy: We must decide whether a landfill constructed on non-Indian fee land that falls within the boundaries of the original Yankton Reservation remains subject to federal environmental regulations. If the divestiture of Indian property in 1894 effected a diminishment of Indian territory, then the ceded lands no longer constitute "Indian country" as defined by 18 U. S. C. § 1151(a), and the State now has primary jurisdiction over them. In light of the operative language of the 1894 Act, and the circumstances surrounding its passage, we hold that Congress intended to diminish the Yankton Reservation and consequently that the waste site is not in Indian country.
I A
At the outset of the 19th century, the Yankton Sioux Tribe held exclusive dominion over 13 million acres of land between the Des Moines and Missouri Rivers, near the boundary that currently divides North and South Dakota. H. Hoover, The Yankton Sioux 25 (1988). In 1858, the
Frankie Sue Del Papa of Nevada, Jan Graham of Utah, and William U. Hill of Wyoming. Yanktons entered into a treaty with the United States renouncing their claim to more than 11 million acres of their aboriginal lands in the north-central plains. Treaty of Apr. 19, 1858, 11 Stat. 743. Pursuant to the agreement, the Tribe ceded"all the lands now owned, possessed, or claimed by them, wherever situated, except four hundred thousand acres thereof, situated and described as follows, to wit-Beginning at the mouth of the Naw-izi-wa-koo-pah or Chouteau River and extending up the Missouri River thirty miles; thence due north to a point; thence easterly to a point on the said Chouteau River; thence down said river to the place of beginning, so as to include the said quantity of four hundred thousand acres." Art. I, id., at 744.
The retained portion of the Tribe's lands, located in what is now the southeastern part of Charles Mix County, South Dakota, was later surveyed and determined to encompass 430,405 acres. See Letter from the Commissioner of Indian Affairs to the Secretary of the Interior (Dec. 9, 1893), reprinted in S. Exec. Doc. No. 27, 53d Cong., 2d Sess., 5 (1894) (hereinafter Letter). In consideration for the cession of lands and release of claims, the United States pledged to protect the Yankton Tribe in their "quiet and peaceable possession" of this reservation and agreed that "[n]o white person," with narrow exceptions, would "be permitted to reside or make any settlement upon any part of the [reservation]." Arts. IV, X, 11 Stat. 744, 747. The Federal Government further promised to pay the Tribe, or expend for the benefit of members of the Tribe, $1.6 million over a 50-year period, and appropriated an additional $50,000 to aid the Tribe in its transition to the reservation through the purchase of livestock and agricultural implements, and the construction of houses, schools, and other buildings. Not all of this assistance was forthcoming, and the Tribe experienced severe financial difficulties in the years that followed, compounded by weather cycles of drought and devastating floods. When war broke out between the United States and the Sioux Nation in 1862, the Yankton Tribe alone sided with the Federal Government, a decision that isolated it from the rest of the Sioux Federation and caused severe inner turmoil as well. The Tribe's difficulties coincided with a period of rapid growth in the United States' population, increasing westward migration, and ensuing demands from non-Indians to open Indian holdings throughout the Western States to settlement.
In response to these "familiar forces," DeCoteau v. District County Court for Tenth Judicial Dist., 420 U. S. 425, 431 (1975), Congress retreated from the reservation concept and began to dismantle the territories that it had previously set aside as permanent and exclusive homes for Indian tribes. See Solem v. Bartlett, 465 U. S. 463, 466 (1984). The pressure from westward-bound homesteaders, and the belief that the Indians would benefit from private property ownership, prompted passage of the Dawes Act in 1887, 24 Stat. 388. The Dawes Act permitted the Federal Government to allot tracts of tribal land to individual Indians and, with tribal consent, to open the remaining holdings to non-Indian settlement. Within a generation or two, it was thought, the tribes would dissolve, their reservations would disappear, and individual Indians would be absorbed into the larger community of white settlers. See Hearings on H. R. 7902 before the House Committee on Indian Affairs, 73d Cong., 2d Sess., 428 (1934) (statement of D. S. Otis on the history of the allotment policy). With respect to the Yankton Reservation in particular, some Members of Congress speculated that "close contact with the frugal, moral, and industrious people who will settle [on the reservation] [would] stimulate individual effort and make [the Tribe's] progress much more rapid than heretofore." Report of the Senate Committee on Indian Affairs, S. Rep. No. 196, 53d Cong., 2d Sess., 1 (1894).
In accordance with the Dawes Act, each member of the Yankton Tribe received a 160-acre tract from the existing reservation, held in trust by the United States for 25 years. Members of the Tribe acquired parcels of land throughout the 1858 reservation, although many of the allotments were clustered in the southern part, near the Missouri River. By 1890, the allotting agent had apportioned 167,325 acres of reservation land, 95,000 additional acres were subsequently allotted under the Act of February 28, 1891, 26 Stat. 795, and a small amount of acreage was reserved for government and religious purposes. The surplus amounted to approximately 168,000 acres of unallotted lands. See Letter, at 5.
In 1892, the Secretary of the Interior dispatched a threemember Yankton Indian Commission to Greenwood, South Dakota, to negotiate for the acquisition of these surplus lands. See Act of July 13, 1892, 27 Stat. 137 (appropriating funds to enable the Secretary to "negotiate with any Indians for the surrender of portions of their respective reservations"). When the Commissioners arrived on the reservation in October 1892, they informed the Tribe that they had been sent by the "Great Father" to discuss the cession of "this land that [members of the Tribe] hold in common," Council of the Yankton Indians (Oct. 8, 1892), transcribed in S. Exec. Doc. No. 27, at 48, and they abruptly encountered opposition to the sale from traditionalist tribal leaders. See Report of the Yankton Indian Commission (Mar. 31, 1893), reprinted in S. Exec. Doc. No. 27, at 9-11 (hereinafter Report). In the lengthy negotiations that followed, members of the Tribe raised concerns about the suggested price per acre, the preservation of their annuities under the 1858 Treaty, and other outstanding claims against the United States, but they did not discuss the future boundaries of the reservation. Once the Commissioners garnered a measure of support for the sale of the unallotted lands, they submitted a proposed agreement to the Tribe.1
"Article I.
"The Yankton tribe of Dakota or Sioux Indians hereby cede, sell, relinquish, and convey to the United States all their claim, right, title, and interest in and to all the unallotted lands within the limits of the reservation set apart to said Indians as aforesaid.
"Article II.
"In consideration for the lands ceded, sold, relinquished, and conveyed to the United States as aforesaid, the United States stipulates and agrees to pay to the said Yankton tribe of Sioux Indians the sum of six hundred thousand dollars ($600,000), as hereinbefore provided for.
"Article VII.
"In addition to the stipulations in the preceding articles, upon the ratification of this agreement by Congress, the United States shall pay to the Yankton tribe of Sioux Indians as follows: To each person whose name is signed to this agreement and to each other male member of the tribe who is eighteen years old or older at the date of this agreement, twenty dollars ($20) in one double eagle, struck in the year 1892 as a memorial of this agreement….
"Article VIII.
"Such part of the surplus lands hereby ceded and sold to the United States as may now be occupied by the United States for agency, schools, and other purposes, shall be reserved from sale to settlers until they are no longer required for such purposes. But all other lands included in this sale shall, immediately after the ratification of this agreement by Congress, be offered for sale through the proper land office, to be disposed of under the existing land laws of the United States, to actual bona fide settlers only.
"Article XV.
"The claim of fifty-one Yankton Sioux Indians, who were employed as scouts by General Alf. Sully in 1864, for additional compensation at the rate of two hundred and twenty-five dollars ($225) each, aggregating the sum of eleven thousand four hundred and seventy-five dollars ($11,475) is hereby recognized as just, and within ninety days (90) after the ratification Article I of the agreement provided that the Tribe would "cede, sell, relinquish, and convey to the United States" all of the unallotted lands on the reservation. Pursuant to Article II, the United States agreed to compensate the Tribe in a single payment of $600,000, which amounted to $3.60 per acre.2 Much of the agreement focused on the payment and disposition of that sum. Article VII further provided that all the signatories and adult male members of the Tribe would receive a $20 gold piece to commemorate the agreement. Some members of the Tribe also sought unpaid wages from their service as scouts in the Sioux War, and in Article XV; the United States recognized their claim. The saving clause in Article XVIII, the core of the current disagreement between the parties to this case, stated that noth
of this agreement by Congress the same shall be paid in lawful money of the United States to the said scouts or to their heirs.
"Article XVII.
"No intoxicating liquors nor other intoxicants shall ever be sold or given away upon any of the lands by this agreement ceded and sold to the United States, nor upon any other lands within or comprising the reservations of the Yankton Sioux or Dakota Indians as described in the treaty between the said Indians and the United States, dated April 19th, 1858, and as afterwards surveyed and set off to the said Indians. The penalty for the violation of this provision shall be such as Congress may prescribe in the act ratifying this agreement.
"Article XVIII.
"Nothing in this agreement shall be construed to abrogate the treaty of April 19th, 1858, between the Yankton tribe of Sioux Indians and the United States. And after the signing of this agreement, and its ratification by Congress, all provisions of the said treaty of April 19th, 1858, shall be in full force and effect, the same as though this agreement had not been made, and the said Yankton Indians shall continue to receive their annuities under the said treaty of April 19th, 1858." 28 Stat. 314-318. ing in the agreement's terms "shall be construed to abrogate the treaty [of 1858]" and that "all provisions of the said treaty… shall be in full force and effect, the same as though this agreement had not been made."
By March 1893, the Commissioners had collected signatures from 255 of the 458 male members of the Tribe eligible to vote, and thus obtained the requisite majority endorsement. The Yankton Indian Commission filed its report in May 1893, but congressional consideration was delayed by an investigation into allegations of fraud in the procurement of signatures. On August 15, 1894, Congress finally ratified the 1892 agreement, together with similar surplus land sale agreements between the United States and the Siletz and Nez Perce Tribes. Act of Aug. 15, 1894, 28 Stat. 286. The 1894 Act incorporated the 1892 agreement in its entirety and appropriated the necessary funds to compensate the Tribe for the ceded lands, to satisfy the claims for scout pay, and to award the commemorative $20 gold pieces. Congress also prescribed the punishment for violating a liquor prohibition included in the agreement and reserved certain sections in each township for common-school purposes. Ibid.
President Cleveland issued a proclamation opening the ceded lands to settlement as of May 21,1895, and non-Indians rapidly acquired them. By the turn of the century, 90 percent of the unallotted tracts had been settled. See Yankton Sioux Tribe v. United States, 623 F.2d 159, 171 (Ct. Cl. 1980). A majority of the individual allotments granted to members of the Tribe also were subsequently conveyed in fee by the members to non-Indians. Today, the total Indian holdings in the region consist of approximately 30,000 acres of allotted land and 6,000 acres of tribal land. Indian Reservations: A State and Federal Handbook 260 (1986).
Although formally repudiated with the passage of the Indian Reorganization Act in 1934, 48 Stat. 984, 25 U. S. C. § 461, the policy favoring assimilation of Indian tribes through the allotment of reservation land left behind a last ing legacy. The conflict between the modern-day approach to tribal self-determination and the assimilation impetus of the allotment era has engendered "a spate of jurisdictional disputes between state and federal officials as to which sovereign has authority over lands that were opened by the [surplus land] Acts and have since passed out of Indian ownership." Solem, 465 U. S., at 467.
B
We confront such a dispute in the instant case, in which tribal, federal, and state officials disagree as to the environmental regulations applicable to a proposed waste site. In February 1992, several South Dakota counties formed the Southern Missouri Recycling and Waste Management District (hereinafter Waste District) for the purpose of constructing a municipal solid waste disposal facility. The Waste District acquired the site for the landfill, which falls within the 1858 boundaries of the Yankton Sioux Reservation, in fee from a non-Indian. The predicate for the parties' claims in this case is that the waste site lies on land ceded in the 1894 Act, and the record supports that assumption.
In the Tribe's complaint, the proposed landfill is described as "the south one-half north one-quarter (S% N'i4), Section 6, Township 96 North, Range 65 West (S6, T96N, R65W) of the Fifth Principal Meridan [sic], Charles Mix County, South Dakota." App. 24. That description corresponds to the account of a tract of land deeded to Lars K. Langeland under the Homestead Act in 1904. See App. to Brief for Respondent Southern Missouri Waste Management District 1a-2a. Because all of the land allotted to individual Indians on the Yankton Reservation was inalienable, pursuant to the Dawes Act, during a 25-year trust period, the tract acquired by a homesteader in 1904 and currently owned by the Waste District must consist of unallotted land ceded in the 1894 Act. (The Dawes Act was amended in 1906 by the Burke Act, 34 Stat. 182, 25 U. S. C. § 349, which permitted the issuance of some fee-simple patents before the expiration of the 25-year trust period, but the restrictions on alienation remained in place as of 1904.)
When the Waste District sought a state permit for the landfill, the Yankton Tribe intervened and objected on environmental grounds, arguing that the proposed compacted clay liner was inadequate to prevent leakage. After an administrative hearing in December 1993, the State Board of Minerals and the Environment granted the solid waste permit, finding that South Dakota regulations did not require the installation of the synthetic composite liner the Tribe had requested. The Sixth Judicial Circuit affirmed the Board's decision, and no appeal was taken to the State Supreme Court.
In September 1994, the Tribe filed suit in the Federal District Court for the District of South Dakota to enjoin construction of the landfill, and the Waste District joined South Dakota as a third party so that the State could defend its jurisdiction to grant the permit. The Tribe also sought a declaratory judgment that the permit did not comport with Federal Environmental Protection Agency (EP A) regulations mandating the installation of a composite liner in the landfill. See 40 CFR § 258.40(b) (1997). The District Court held, in accordance with our decision in South Dakota v. Bourland, 508 U. S. 679, 692 (1993), that the Tribe itself could not assert regulatory jurisdiction over the non-Indian activity on fee lands. Furthermore, because the Tribe did not establish that the landfill would compromise the "political integrity, the economic security, or the health or welfare of the tribe," the court concluded that the Tribe could not invoke its inherent sovereignty under the exceptions in Mon tana v. United States, 450 U. S. 544, 566 (1981). Accordingly, the court declined to enjoin the landfill project, a decision the Tribe does not appeal. The District Court also determined, however, that the 1894 Act did not diminish the exterior boundaries of the reservation as delineated in the 1858 Treaty between the United States and the Tribe, and consequently that the waste site lies within an Indian reservation where federal environmental regulations apply.
On appeal by the State,3 a divided panel of the Court of Appeals for the Eighth Circuit agreed that "Congress intended by its 1894 Act that the Yankton Sioux sell their surplus land to the government, but not their governmental authority over it." 99 F.3d 1439, 1457 (1996). The court relied primarily on the saving clause in Article XVIII, reasoning that, given its "unusually expansive language," other sections of the 1894 Act "should be read narrowly to minimize any conflict with the 1858 treaty." Id., at 1447. The court further concluded that neither the historical evidence nor the demographic development of the area could sustain a finding of diminishment. Id., at 1457.
We granted certiorari to resolve a conflict between the decision of the Court of Appeals and a number of decisions of the South Dakota Supreme Court declaring that the reservation has been diminished.4 520 U. S. 1263 (1997). We now reverse the Eighth Circuit's decision and hold that the unallotted lands ceded as a result of the 1894 Act did not retain reservation status.
Thompson, 355 N. W. 2d 349, 350 (S. D. 1984); State v. Williamson, 87 S. D. 512, 515, 211 N. W. 2d 182, 184 (1973); Wood v. Jameson, 81 S. D. 12, 18-19, 130 N. W. 2d 95, 99 (1964). II
States acquired primary jurisdiction over unallotted opened lands where "the applicable surplus land Act freed that land of its reservation status and thereby diminished the reservation boundaries." Solem, 465 U. S., at 467. In contrast, if a surplus land Act "simply offered non-Indians the opportunity to purchase land within established reservation boundaries," id., at 470, then the entire opened area remained Indian country. Our touchstone to determine whether a given statute diminished or retained reservation boundaries is congressional purpose. See Rosebud Sioux Tribe v. Kneip, 430 U. S. 584, 615 (1977). Congress possesses plenary power over Indian affairs, including the power to modify or eliminate tribal rights. See, e. g., Santa Clara Pueblo v. Martinez, 436 U. S. 49, 56 (1978). Accordingly, only Congress can alter the terms of an Indian treaty by diminishing a reservation, United States v. Celestine, 215 U. S. 278, 285 (1909), and its intent to do so must be "clear and plain," United States v. Dion, 476 U. S. 734, 738-739 (1986).
Here, we must determine whether Congress intended by the 1894 Act to modify the reservation set aside for the Yankton Tribe in the 1858 Treaty. Our inquiry is informed by the understanding that, at the turn of this century, Congress did not view the distinction between acquiring Indian property and assuming jurisdiction over Indian territory as a critical one, in part because "[t]he notion that reservation status of Indian lands might not be coextensive with tribal ownership was unfamiliar," Solem, 465 U. S., at 468, and in part because Congress then assumed that the reservation system would fade over time. "Given this expectation, Congress naturally failed to be meticulous in clarifying whether a particular piece of legislation formally sliced a certain parcel of land off one reservation." Ibid.; see also Hagen v. Utah, 510 U. S. 399, 426 (1994) (Blackmun, J., dissenting) ("As a result of the patina history has placed on the allotment Acts, the Court is presented with questions that their architects could not have foreseen"). Thus, although "[t]he most probative evidence of diminishment is, of course, the statutory language used to open the Indian lands," we have held that we will also consider "the historical context surrounding the passage of the surplus land Acts," and, to a lesser extent, the subsequent treatment of the area in question and the pattern of settlement there. Id., at 411. Throughout this inquiry, "we resolve any ambiguities in favor of the Indians, and we will not lightly find diminishment." Ibid.
A
Article I of the 1894 Act provides that the Tribe will "cede, sell, relinquish, and convey to the United States all their claim, right, title, and interest in and to all the unallotted lands within the limits of the reservation"; pursuant to Article II, the United States pledges a fixed payment of $600,000 in return. This "cession" and "sum certain" language is "precisely suited" to terminating reservation status. See DeCoteau, 420 U. S., at 445. Indeed, we have held that when a surplus land Act contains both explicit language of cession, evidencing "the present and total surrender of all tribal interests," and a provision for a fixed-sum payment, representing "an unconditional commitment from Congress to compensate the Indian tribe for its opened land," a "nearly conclusive," or "almost insurmountable," presumption of diminishment arises. Solem, supra, at 470; see also Hagen, supra, at 411.
The terms of the 1894 Act parallel the language that this Court found terminated the Lake Traverse Indian Reservation in DeCoteau, supra, at 445, and, as in DeCoteau, the 1894 Act ratified a negotiated agreement supported by a majority of the Tribe. Moreover, the Act we construe here more clearly indicates diminishment than did the surplus land Act at issue in Hagen, which we concluded diminished reservation lands even though it provided only that "all the unallotted lands within said reservation shall be restored to the public domain." See 510 U. S., at 412.
The 1894 Act is also readily distinguishable from surplus land Acts that the Court has interpreted as maintaining reservation boundaries. In both Seymour v. Superintendent of Wash. State Penitentiary, 368 U. S. 351, 355 (1962), and Mattz v. Arnett, 412 U. S. 481, 501-502 (1973), we held that Acts declaring surplus land "subject to settlement, entry, and purchase," without more, did not evince congressional intent to diminish the reservations. Likewise, in Solem, we did not read a phrase authorizing the Secretary of the Interior to "sell and dispose" of surplus lands belonging to the Cheyenne River Sioux as language of cession. See 465 U. S., at 472. In contrast, the 1894 Act at issue here-a negotiated agreement providing for the total surrender of tribal claims in exchange for a fixed payment-bears the hallmarks of congressional intent to diminish a reservation.
B
The Yankton Tribe and the United States, appearing as amicus for the Tribe, rest their argument against diminishment primarily on the saving clause in Article XVIII of the 1894 Act. The Tribe asserts that because that clause purported to conserve the provisions of the 1858 Treaty, the existing reservation boundaries were maintained. The United States urges a similarly "holistic" construction of the agreement, which would presume that the parties intended to modify the 1858 Treaty only insofar as necessary to open the surplus lands for settlement, without fundamentally altering the treaty's terms.
Such a literal construction of the saving clause, as the South Dakota Supreme Court noted in State v. Greger, 559 N. W. 2d 854, 863 (1997), would "impugn the entire sale." The unconditional relinquishment of the Tribe's territory for settlement by non-Indian homesteaders can by no means be reconciled with the central provisions of the 1858 Treaty, which recognized the reservation as the Tribe's "permanent" home and prohibited white settlement there. See Oregon Dept. of Fish and Wildlife v. Klamath Tribe, 473 U. S. 753, 770 (1985) (discounting a saving clause on the basis of a "glaring inconsistency" between the original treaty and the subsequent agreement). Moreover, the Government's contention that the Tribe intended to cede some property but maintain the entire reservation as its territory contradicts the common understanding of the time: that tribal ownership was a critical component of reservation status. See Solem, supra, at 468. We "cannot ignore plain language that, viewed in historical context and given a fair appraisal, clearly runs counter to a tribe's later claims." Klamath, supra, at 774 (internal quotation marks and citation omitted).
Rather than read the saving clause in a manner that eviscerates the agreement in which it appears, we give it a "sensible construction" that avoids this "absurd conclusion." See United States v. Granderson, 511 U. S. 39, 56 (1994) (internal quotation marks omitted). The most plausible interpretation of Article XVIII revolves around the annuities in the form of cash, guns, ammunition, food, and clothing that the Tribe was to receive in exchange for its aboriginal claims for 50 years after the 1858 Treaty. Along with the proposed sale price, these annuities and other unrealized Yankton claims dominated the 1892 negotiations between the Commissioners and the Tribe. The tribal historian testified, before the District Court, that the loss of their rations would have been "disastrous" to the Tribe, App. 589, and members of the Tribe clearly perceived a threat to the annuities. At a particularly tense point in the negotiations, when the tide seemed to turn in favor of forces opposing the sale, Commissioner John J. Cole warned:"I want you to understand that you are absolutely dependent upon the Great Father to-day for a living. Let the Government send out instructions to your agent to cease to issue these rations, let the Government instruct your agent to cease to issue your clothes…. Let the Government instruct him to cease to issue your supplies, let him take away the money to run your schools with, and I want to know what you would do. Everything you are wearing and eating is gratuity. Take all this away and throw this people wholly upon their own responsibility to take care of themselves, and what would be the result? Not one-fourth of your people could live through the winter, and when the grass grows again it would be nourished by the dust of all the balance of your noble tribe." Council of the Yankton Indians (Dec. 10, 1892), transcribed in S. Exec. Doc. No. 27, at 74.
Given the Tribe's evident concern with reaffirmance of the Government's obligations under the 1858 Treaty, and the Commissioners' tendency to wield the payments as an inducement to sign the agreement, we conclude that the saving clause pertains to the continuance of annuities, not the 1858 borders.
The language in Article XVIII specifically ensuring that the "Yankton Indians shall continue to receive their annuities under the [1858 Treaty]" underscores the limited purpose and scope of the saving clause. It is true that the Court avoids interpreting statutes in a way that "renders some words altogether redundant." Gustafson v. Alloyd Co., 513 U. S. 561, 574 (1995). But in light of the fact that the record of the negotiations between the Commissioners and the Yankton Tribe contains no discussion of the preservation of the 1858 boundaries but many references to the Government's failure to fulfill earlier promises, see, e. g., Council of the Yankton Indians (Dec. 3, 1892), transcribed in S. Exec. Doc. No. 27, at 54-55, it seems most likely that the parties inserted and understood Article XVIII, including both the general statement regarding the force of the 1858 Treaty and the particular provision that payments would continue as specified therein, to assuage the Tribes' concerns about their past claims and future entitlements. Indeed, apart from the pledge to pay annuities, it is hard to identify any provision in the 1858 Treaty that the Tribe might have sought to preserve, other than those plainly inconsistent with or expressly included in the 1894 Act. The Government points to Article XI of the treaty, in which the Tribe agreed to submit for federal resolution "all matters of dispute and difficulty between themselves and other Indians," 11 Stat. 747, and urges us to extrapolate from this provision that the Tribe implicitly retained jurisdiction over internal matters, and from there to apply the standard canon of Indian law that "[o]nce powers of tribal self-government or other Indian rights are shown to exist, by treaty or otherwise, later federal action which might arguably abridge them is construed narrowly in favor of retaining Indian rights." F. Cohen, Handbook of Federal Indian Law 224 (1982) (hereinafter Cohen). But the treaty's reference to tribal authority is indirect, at best, and it does not persuade us to view the saving clause as an agreement to maintain exclusive tribal governance within the original reservation boundaries.
The Tribe further contends that because Article XVIII affirms that the 1858 Treaty will govern "the same as though [the 1892 agreement] had not been made," without reference to consistency between those agreements, it has more force than the standard saving clause. While the language of the saving clause is indeed unusual, we do not think it is meaningfully distinct from the saving clauses that have failed to move this Court to find that pre-existing treaties remain in effect under comparable circumstances. See, e. g., Klamath, 473 U. S., at 769-770; Montana, 450 U. S., at 548, 558-559; Rosebud, 430 U. S., at 623 (Marshall, J., dissenting). Furthermore, "it is a commonplace of statutory construction that the specific" cession and sum certain language in Articles I and II "governs the general" terms of the saving clause. See Morales v. Trans World Airlines, Inc., 504 U. S. 374, 384 (1992). Finally, the Tribe argues that, at a minimum, the saving clause renders the statute equivocal, and that confronted with that ambiguity we must adopt the reading that favors the Tribe. See Carpenter v. Shaw, 280 U. S. 363, 367 (1930). The principle