delivered the opinion of the Court.
The issue is whether the judicially created doctrine of tribal-court exhaustion, requiring a district court to stay its hand while a tribal court determines its own jurisdiction, should apply in this case, which if brought in a state court would be subject to removal. We think the exhaustion doctrine should not extend so far.
I
With the object of “encouraging] the private sector to become involved in the development of atomic energy for peaceful purposes,”
Duke Power Co.
v.
Carolina Environmental Study Group, Inc.,
wake of the 1979 accident at the Three Mile Island nuclear power plant, suits proliferated in state and federal courts, but because the accident was not an “extraordinary nuclear occurrence,” within the meaning of the Act, see §2014(j), there was no mechanism for consolidating the claims in federal court. See S. Rep. No. 100-218, p. 13 (1987). Congress respоnded in 1988 by amending the Act to grant United States district courts original and removal jurisdiction over all “public liability actions,” 102 Stat. 1076, 42 U. S. C. §2210(n)(2), defined as suits “asserting public liability,” §2014(hh), which “shall be deemed to be ... aetion[s] arising under” § 2210. The Act now provides the mechanics for consolidating such actions, §2210(n)(2), for managing them once consolidated, §2210(n)(3), and for distributing limited compensatory funds, §2210(o).
Neztsosie, two members of the Navajo Nation, filed suit in the District Court of the Navajo Nation, Tuba City District, against petitioner El Paso Natural Gas Company and one of its subsidiaries, Rare Metals Corporation. The Neztsosies alleged that on the Navajo Nation Reservation, from 1950 to 1965, El Paso and Rare Metals operated open pit uranium mines, which collected water then used by the Neztsosies for a number of things, including drinking. The Neztsosies claimed that, as a result, they suffered severe injuries from exposure to radioactive and other hazardous matеrials, for whieh they sought compensatory and punitive damages under Navajo tort law. App. 18a-27a. In 1996, respondent Zonnie Richards, also a member of the Navajo Nation, brought suit for herself and her husband’s estate in the District Court of the
*478
Navajo Nation, Kayenta District, against defendants including the Vanadium Corporation of America (VCA), predecessor by merger of petitioner Cyprus Foote Mineral Company. Richards raised Navajo tort law claims for wrongful death and loss of consortium arising from uranium mining and processing on the Navajo Nation Reservation by VCA and other defendants from the 1940’s through the 1960’s.
El Paso and Cyprus Foote States District Court for the District of Arizona, seeking to enjoin the Neztsosies and Richards from pursuing their claims in the Tribal Courts. The District Court, citing the tribal-court exhaustion doctrine of
National Farmers Union Ins. Cos.
v.
Crow Tribe,
On the affirmed the District Court’s decisions declining to enjoin the Neztsosies and Richards from pursuing non-Price-Anderson Act claims, as well as the decisions to аllow the Tribal Courts to decide in the first instance whether the Neztsosies’ and Richards’s tribal claims fell within the ambit of the Price-Anderson Act.
* — I > — (
There is one matter preliminary to the principal issue. Because respondents did not aрpeal those portions of the District Court’s orders enjoining them from pursuing Price-Anderson Act claims in Tribal Court, those injunctions were not properly before the Court of Appeals, which consequently erred in addressing them. We have repeatedly affirmed two linked principles governing the consequences of an appellee’s failure to cross-appeal. Absent a eross-appeal, an appellee may “urge in support of a decree any matter appearing in the record, although his argument may involve an attack upon the reasoning of the lower court,” but may not “attack the decree with a view either to enlarging his own rights thereunder or of lessening the rights of his adversary.”
United States
v.
American Railway Express Co,,
The Court of Appeals acknowledged the rule, but, in light of the natural temptation to dispose of the related questions of jurisdiction and exhaustion at one blow, still thought it could take up the unappealed portions of the District Court’s orders
sua sponte
because “important comity considera
*480
tions” were involved.
*481 On the assumption that comity is not enough, respondents offer one additional justification for an exception to the cross-appeal requirement here. They point out that the District Court orders appealed from were preliminary injunctions and thus interlocutory, not final, decrees. Respondents contend that because they knew they could challenge the substance of those orders on appeal from a final judgment, they should not be penalized for failing to cross-appeal at this preliminary stage of the suit. But this argument misconceives the nature of the cross-aрpeal requirement. It is not there to penalize parties who fañ to assert their rights, but is meant to protect institutional interests in the orderly *482 functioning of the judicial system, by putting opposing parties and appellate courts on notice of the issues to be litigated and encouraging repose of those that are not. Fairness of notice does not turn on the interlocutory character of the orders at issue here, and while the interest in rеpose is somewhat diminished when a final appeal may yet raise the issue, it is still considerable owing to the indefinite duration of the injunctions. Preliminary injunctions are, after all, appeal-able as of right, see 28 U. S. C. § 1292(a)(1), and the timely filing requirements of Federal Rules of Appellate Procedure 4 and 26(b) squarely cover such appeals. Neither those Rules nor the interests animating the cross-appeal requirement offer any leeway for such an exception.
hH
Before the District Court, petitioners asserted simply that the Tribal Court lacked subject-matter jurisdiction over Price-Anderson Act claims in respondents’ tribal-court suits, see App. 14a, 15a, 37a, and sought injunctive relief.
4
The District Court responded by enjoining respondents from pursuing any Price-Anderson claims in Tribal Court, and because they did not appeal the injunction, we have no occasion
*483
to consider its merits.
5
Yet the injunction has no practical significance without a determination whether respondents’ causes of action are as a matter of law Price-Anderson claims under the terms of 42 U. S. C. §§ 2210(h)(2) and 2014(hh). This question the District Court declined to answer, thinking that the doctrine of tribal-court exhaustion required it to abstain from deciding a question of tribal-court jurisdiction until the Tribal Courts themselves had addressed the matter. The Court of Appeals approved the abstention on the theory that the comity rationale undеrlying the tribal exhaustion doctrine applied. See
National Farmers Union Ins. Cos.
v.
Crow Tribe,
This case differs markedly. provision, see 42 U. S. C. § 2014(hh), 6 the Price-Anderson Act transforms into a federal action “any public liability action arising out of or resulting from a nuclear incident,” § 2210(n)(2). The Act not only gives a district court original jurisdiction over such a claim, see ibid., but provides for removal to a federal court as of right if a putative Price-Anderson action is brought in a state court, see ibid. Congress thus expressed an unmistakable preference for a federal forum, at the behest of the defending party, both for *485 litigating a Priee-Anderson claim on the merits and for determining whether a claim falls under Price-Anderson when removal is contested.
Petitioners seek the benefit of what in effect is the same scheme of preference for a federal forum when they ask for an injunction against further litigation in the tribal courts. To be sure, their complaints claimed that the tribal courts (unlike state courts) had no jurisdiction over these actions, on the ground that they were Price-Anderson claims. But petitioners unmistakably seek to enjoin litigation of these claims in the tribal courts, whether or not those courts would have jurisdiction to exercise in the absence of objection. Injunction against further litigation in tribal courts would in practical terms give the same result as a removal held to be justified on the ground that the actions removed fell under the Priee-Anderson definitions of claims of public liability: if respondents then should wish to proceed they would be forced to refile their claims in federal court (or a state court from which the claims would be removed). The issue, then, is whether Congress would have chosen to postpone federal resolution of the enjoinable character of this tribal-court litigation, when it would not have postponed federal resolution of the functionally identical issue pending in a state court.
any reason that Congress would have favored tribal exhaustion. Any generalized sense of comity toward nonfederal courts is obviously displaced by the provisions for preemption and removal from state courts, which are thus accorded neither jot nor tittle of deference. 7 The apparent reasons for this congressional *486 policy of immediate access to federal forums are as much applicsible to tribal- as to state-court litigation.
The Act provides clear aims of speed and efficiency. Section 2210(n)(3)(A) empowers the chief judge of a district court to appoint a special caseload management рanel to oversee cases arising from a nuclear incident. The functions of such panels include case consolidation, §2210(n)(3)(C)(i); setting of priorities, §2210(n)(3)(C)(ii); “promulgation] [of] special rules of court... to expedite cases or allow more equitable consideration of claims,” §2210(n)(3)(C)(v); and implementation of such measures “as will encourage the equitable, prompt, and efficient resolution of cases arising out of the nuclear incidеnt,” § 2210(n)(3)(C)(vi).
The terms of the are history, which expressly refers to the multitude of separate cases brought “in various state and Federal courts” in the aftermath of the Three Mile Island accident. See S. Rep. No. 103-218, at 13. This history adverts to the expectation that “the provisions for consolidation of claims in the event of any nuclear incident... would avoid the inefficiencies resulting from duplicative determinations of similar issues in multiple jurisdictions that may occur in the absence of consolidation.” Ibid.
Applying tribal exhaustion would chief of “duplicative determinations” and consequent “inefficiencies” that the Act sought to avoid, and the force of the congressional concerns saps the two arguable justifications for applying tribal exhaustion of any plausibility in these circumstances. The first possible justification might be that tribal exhaustion is less troubling than state-court exhaustion, because in the former situаtion the district court may review jurisdiction after recourse to tribal court has been exhausted, see National Farmers Union Ins. Cos., 471 U. S., *487 at 857, whereas a state court’s determination of its jurisdiction is final except for the possibility of our review on certio-rari. But the likelihood of effective review says nothing to the Act’s insistence on efficient disposition of public liability claims, which would of course be curtailed by an exhaustion requirement. It is not credible that Congress would have uniquely countenanced, let alone chosen, such a delay when public liability claims are brought in tribal court.
justification is that the absence of any statutory provision for removal from tribal court running parallel to the terms authorizing state-court removal might ground a negative inference against any intent to govern Price-Anderson actions in tribal courts, in accordance with the usual policy of letting a plaintiff choose the forum. But only the most zealous application of the maxim expressio unius est exclusio alterius could answer the implausibility that Congress would have intended to force defendants to remain in tribal courts. The congressional reasoning sketched above is ho less forceful when plaintiffs choose tribal courts; leaving such claims in these courts would just as effectively thwart the Act’s policy of getting such cases into a federal forum for consolidation, as leaving them in state forums would do.
Why, then, the congressional silence on tribal courts? If “expressio mdus ...” fails to explаin the Congress’s failure to provide for tribal-court removal, what is the explanation? After all we have said, inadvertence seems the most likely. We have not been told of any nuclear testing laboratories or reactors on reservation lands, and if none was brought to the attention of Congress either, Congress probably would never have expected an occasion for asserting tribal jurisdiction over claims like these. Now and then silence is not pregnant.
comity rationale for tribal exhaustion normally appropriate to a tribal court’s determination of its jurisdiction stops short of the Price-Anderson Act, the District *488 Court should have decided whether respondents’ claims constituted “public liability actionfe] arising out of or resulting from a nuclear incident,” 42 U. S. C. § 2210(n)(2). We accordingly vacate the judgment of the Court of Appeals and remand with instructions to remand the case to the District Court fоr proceedings consistent with this opinion.
So ordered.
Notes
“Source material” includes uranium and uranium ore. 42 U.S.C. § 2014(z). “Byproduct material” includes “the tailings or wastes produced by the extraction or concentration of uranium or thorium from any ore processed primarily for its source material content.” § 2014(e).
The issue has caused much disagreement among the Courts of Appeals and even inconsistency within particular Circuits for more than 50 years. For a survey of many of the cases, see
Marts
v.
Hines,
On three in dictum that might be taken to suggest the possibility of exceptions to the rule. Only one of those statements concerned the power of the courts of appeals. See
Bowen
v.
Postal Service,
expressed the rule in emphatic terms, see,
e.g., Helvering
v.
Pfeiffer,
At oral argument before the Court of Appeals, petitioners introduced for the first time the essence of the theory on which they now rely, that the Tribal Courts somehow lacked jurisdiction over Price-Anderson claims because under
Strate
v.
A-1 Contractors,
Although we do not reach the merits of the injunction, candor requires acknowledging that our view of the inappropriateness of applying tribal exhaustion, adumbrated infra, at 485-487, suggests that, notwithstanding the silence of the Price-Anderson Act with respect to tribal courts, the exercise of tribal jurisdiction over claims found to fall within the Act once a defendаnt has sought a federal forum would be anomalous at best.
This structure, in which a public liability action becomes a federal action, but one decided under substantive state-law rules of decision that do not conflict with the Price-Anderson Act, see 42 U. S. C. §2014(hh), resembles what we have spoken of as “'complete pre-emption’ doctrine,” see
Caterpillar Inc.
v.
Williams,
This is not to say that the existence of a federal preemption defense in the more usual sense would affect the logic of tribal exhaustion. Under normal circumstances, tribal courts, like state courts, can and do decide questions of federal law, and there is no reason to think that questions of federal preemption are any different. See
Santa Clara Pueblo
v.
Martinez,
