I
FACTS AND PROCEEDINGS BELOW
These consolidated interlocutory appeals and appeals as-of-right arise from a suit filed in 1979 by the National Audubon Society and others (“Audubon”) against the Los Angeles Department of Water and Power (“DWP”) to restrain DWP’s diversion to Los Angeles of four freshwater streams that would otherwise flow into Mono Lake.
Mono Lake is a natural saline lake located wholly within the State of California. Pursuant to permits granted by the California Water Resources Control Board, DWP has carried out these diversions since 1940. With the diversion of the Lake’s surface water sources, its natural volume has been decreased and some 14,000 acres of lake bed have been exposed. The reduction of the Lake volume has also caused increases in salinity and ion concentration.
Audubon’s original complaint, filed in the Superior Court for Mono County, asserted: 1) violation of the public trust; 2) violation *1411of California Constitution article XVI, section 6 (prohibiting a gift by the state of a state asset); 3) a quiet title action to establish public trust rights in the waters of the Mono Basin; 4) public and private nuisance (from mud and dust created by reliction); and 5) violation of California Constitution article X, section 4 (prohibiting obstruction of navigable waters). Audubon sought declaratory and injunctive relief.
The case was transferred to Alpine County Superior Court, and DWP filed a cross-complaint containing four counts. The first count sought adjudication of Basin water rights as to all appropriators; the second sought to quiet title to those rights. These two causes named 117 cross-defendants, including all of the plaintiffs, the State of California, the United States Forest Service, the Bureau of Land Management, and numerous private water users. The third cause of action sought a declaration that, to the extent that the United States has jurisdiction over California’s exercise of its navigation trust, Congress has consented to the impairment of the navigable waters of Mono Lake. Finally, DWP asserted that any nuisance at Mono Lake is attributable to the owner of the newly exposed Lake bed, and sought a declaration that conditions at the Lake resulted from a valid exercise of the police power by the State of California.
Thereafter, the United States removed the action to federal district court pursuant to 28 U.S.C. § 1442(a)(1) on the grounds that the cross-complaint implicated acts of the named federal agencies. The district court determined that, although only the third cause of action in DWP’s complaint implicated the acts of federal agencies, the entire action was removable. Accordingly, the court denied DWP’s motion to remand. National Audubon Soc. v. Department of Water and Power, 496 F.Supp. 499 (E.D.Cal.1980).
DWP then made a motion to amend its cross-complaint to drop its third cause of action and filed a concurrent motion to remand to state court on the ground that the original basis for removal had been extinguished. DWP alternatively asked the court to abstain.
At the same time, Audubon sought permission to amend its complaint to include a cause of action based on the federal common law of nuisance. Audubon’s federal nuisance claim was predicated on its assertion that Mono Lake is an “interstate or navigable” water in which there is an overriding federal interest, and that DWP’s diversions were causing, inter alia, water pollution by increasing the Lake’s salinity and ion concentration, and air pollution in the form of alkali dust storms from the newly exposed lake bed. In the same order, the district court granted DWP’s motion to amend its cross-complaint, but also granted Audubon’s motion to add a new federal claim to its complaint. Accordingly, the court denied DWP’s motion to remand.
Shortly thereafter, the district court determined that abstention would be appropriate and instructed Audubon to file an action in state court to resolve two issues: 1) the relationship between the public trust doctrine and the California water rights system, and 2) whether exhaustion of administrative remedies was a prerequisite to Audubon’s suit. The court ruled that it would retain jurisdiction over the case during the pendency of the state action.
Audubon’s state action for declaratory judgment on the two issues in the lower court’s abstention order eventually reached the California Supreme Court. Ruling in favor of Audubon, the court held that the public trust doctrine was not subsumed in the state water rights system and that Audubon was not required to exhaust administrative remedies before the State Water Resources Control Board. National Audubon Society v. Superior Court, 33 Cal.3d 419, 189 Cal.Rptr. 346, 658 P.2d 709, cert. denied sub nom. Los Angeles Dept. of Water & Power v. National Audubon Society, 464 U.S. 977, 104 S.Ct. 413, 78 L.Ed.2d 351 (1983).
The parties returned to federal district court, whereupon DWP, joined by California, filed two motions: the first, a motion for partial summary judgment directed to *1412Audubon’s federal nuisance claims, and the second, a renewed motion for remand to state court on the basis that, if the motion for partial summary judgment were granted, no federal issues would remain to be decided.
In an order dated November 8, 1984, the district courlj granted in part and denied in part DWP’s summary judgment motion. The court held that Audubon could state a federal common law nuisance claim for air pollution caused by dust from the lake bed, and that the air pollution claim was not preempted by the Clean Air Act. The court also held that the water pollution claim was preempted by the Federal Water Pollution Control Act (FWPCA). In addition, the court granted the motion to remand the state law claims to state court, retaining jurisdiction over only the single remaining federal nuisance claim for interstate dust pollution.
By order of April 15, 1984, the district court certified the following three questions for interlocutory appeal: 1) Whether the federal common law nuisance doctrine applies as a basis for restraining the water diversions in this case; 2) Assuming that the federal common law nuisance doctrine applies as a basis for restraining such water diversions, whether the doctrine can be asserted by plaintiffs in this instance; and 3) Whether the district court, having obtained jurisdiction of this matter pursuant to the removal statute of 28 U.S.C. § 1442(a)(1), has discretion to remand this action to the state court after the original basis for removal was deleted in an amendment intended to defeat federal court jurisdiction.
On May 7, 1985, the district court issued a declaratory judgment pursuant to Fed.R. Civ.P. 54(b) on California’s cross-complaint. The court ruled that federal common law of nuisance applies to water diversions authorized under state water rights laws to the extent such diversions cause potential impacts on air quality, but not to the extent that such diversions cause potential impacts on water quality. California and Audubon have appealed this judgment. Audubon, California and DWP have appealed the questions previously certified for interlocutory appeal.
II
ANALYSIS
A. Federal Common Law Nuisance Action
1. Standard of Review
The district court granted summary judgment on the federal common law nuisance claims. We review that decision de novo, Poland v. Martin, 761 F.2d 546, 547 (9th Cir.1985), to determine whether there are any genuine issues of material fact, Fed.R.Civ.P. 56(c), and whether the district court correctly applied the relevant substantive law. Ashton v. Cory, 780 F.2d 816, 818 (9th Cir.1986).
2. Federal Common Law Nuisance Claim — Water Pollution
The district court concluded That Audubon’s federal common law nuisance claim for water pollution is preempted by the FWPCA. In so ruling, the district court relied on the Supreme Court’s statement in Middlesex County Sewerage Authority v. National Sea Clammers Ass’n, 453 U.S. 1, 101 S.Ct. 2615, 69 L.Ed.2d 435 (1981), that “the federal common law of nuisance in the area of water pollution is entirely pre-empted by the more comprehensive scope of the FWPCA, which was completely revised after the decision in Illinois v. Milwaukee.” Id. at 22, 101 S.Ct. at 2627. See Milwaukee v. Illinois, 451 U.S. 304, 101 S.Ct. 1784, 68 L.Ed.2d 114 (1981) (Milwaukee II). The Court’s statement that federal common law nuisance claims for water pollution are preempted by the FWPCA is unequivocal and we affirm the district court’s ruling that this claim is preempted by the FWPCA. See also International Paper Co. v. Ouellette, 479 U.S. 481, 107 S.Ct. 805, 810, 93 L.Ed.2d 883 (1987) (“[T]he Court held that federal legislation now occupied the field, preempting all federal common law.”)
*14133. Federal Common Law Nuisance Claim — Air Pollution
The district court concluded that the federal common law nuisance action based on air pollution could be properly asserted, that it is not preempted by the Clean Air Act, and that Audubon has standing to assert this claim. We hold that Audubon cannot properly assert a federal common law nuisance action based on air pollution.
There is no general federal common law. “Federal courts, unlike state courts, are not general common law courts and do not possess a general power to develop and apply their own rules of decision. Milwaukee II, 451 U.S. at 312, 101 S.Ct. at 1790 (citing Erie R.R. Co. v. Tompkins, 304 U.S. 64, 78, 58 S.Ct. 817, 822, 82 L.Ed. 1188 (1938)). “The enactment of a federal rule in an area of national concern and the decision whether to displace state law in doing so, is generally made not by the federal judiciary, purposefully insulated from democratic pressures, but by the people through their elected representatives in Congress.” Milwaukee II, 451 U.S. at 313, 101 S.Ct. at 1790 (citing Wallis v. Pan American Petroleum Corp., 384 U.S. 63, 68, 86 S.Ct. 1301, 1304, 16 L.Ed.2d 369 (1966)). “ ‘[W]e start with the assumption’ that it is for Congress, not federal courts, to articulate appropriate standards to be applied as a matter of federal law.” Milwaukee II, 451 U.S. at 317, 101 S.Ct. at 1792.
Nonetheless, the Supreme Court has recognized the need and authority of courts to fashion federal common law in a “few and restricted” instances. Texas Industries, Inc. v. Radcliff Materials, Inc., 451 U.S. 630, 640, 101 S.Ct. 2061, 2067, 68 L.Ed.2d 500 (1981), quoting Wheeldin v. Wheeler, 373 U.S. 647, 651, 83 S.Ct. 1441, 1445, 10 L.Ed.2d 605 (1963). “These instances ... fall into essentially two categories: those in which a federal rule of decision is ‘necessary to protect uniquely federal interests,’ Banco Nacional de Cuba v. Sabbatino, 376 U.S. 398, 426, 84 S.Ct. 923, 939, 11 L.Ed.2d 804 (1964), and those in which Congress has given the courts the power to develop substantive law, Wheeldin v. Wheeler, 373 U.S. at 652 [83 S.Ct. at 1445].” Texas Industries, 451 U.S. at 640, 101 S.Ct. at 2067.
We first determine whether Congress has given the courts the power to develop federal substantive law. In the Clean Air Act, 42 U.S.C. § 7401 et seq., Congress established a comprehensive state and federal scheme to control air pollution in the United States. The central elements of this comprehensive scheme are the Act’s provisions for uniform national standards of performance for new stationary sources of air pollution. 42 U.S.C. § 7411. A stationary source of air pollution is expressly limited to any building, structure, facility or installation which emits any air pollution. Id. § 7411(3). The Act’s provisions also provide for uniform national emission standards for hazardous air pollutants likely to cause an increase in mortality or serious illness, id. § 7412, for promulgation of primary and secondary national ambient air quality standards (NAAQS), id. §§ 7408-09, and for the development of national ambient air quality standards for motor vehicle emissions. Id. § 7521.
Two sections of the Clean Air Act govern the establishment and revision of the national ambient air quality standards. Section 108 directs the Administrator of the Environmental Protection Agency (EPA) to identify pollutants which may reasonably be anticipated to endanger public health or welfare and to issue air quality criteria for them. 42 U.S.C. § 7408. Section 109 directs the Administrator to propose and promulgate “primary” and “secondary” NAAQS for pollutants identified under Section 108. 42 U.S.C. § 7409. The Act defines a primary standard as one the attainment and maintenance of which, in the judgment of the Administrator, based on specific criteria and allowing for an adequate margin of safety, is requisite to protect the public health. 42 U.S.C. § 7409. A secondary standard must specify a level of air quality, the attainment of which, in the judgment of the Administrator, based on specific criteria and allowing for an adequate margin of safety, is requisite to protect the public welfare from any known or anticipated adverse effects associated with the presence of the pollutant in the ambient air. Id.
*1414Once the EPA determines that a particular pollutant has an adverse effect on public health or welfare and originates from one or more numerous or diverse mobile or stationary sources, the EPA must develop national air quality standards and the states must implement them within a limited time period. Natural Resources Defense Council, Inc. v. Train, 545 F.2d 320, 322-24 (2nd Cir.1976).
Since 1977, EPA has allowed states with rural fugitive dust areas (RFDA’s) to discount fugitive dust in developing and enforcing a state implementation plan (SIP) for attainment and maintenance of the NAAQS for particulate matter. See 40 C.F.R. § 51.110(f) (1987). On July 1, 1987, the EPA promulgated national ambient air quality standards for particulate matter with an aerometric diameter of a nominal 10 microns or less (PM10). 40 C.F.R. § 50.6(c). Fugitive dust includes PM10 in varying amounts. 52 Fed.Reg. 24716 (July 1, 1987) (Proposed Policy Statement). The EPA has concluded (1) that long time exposure to high concentrations of PM10 constitutes a health risk, and (2) that specific components of PM10 cannot be safely excluded from the primary standard. Id. at 24717. The EPA also promulgated policies and regulations by which it will implement the PM10 NAAQS. 40 C.F.R. §§ 50.6, 50.7 (1987); see 40 C.F.R. Part 50, Appendix J and Appendix K (1987). In accordance with these standards, the EPA categorized areas of the nation into three groups based on the likelihood that the existing state implementation plan must be revised to protect the PM10 NAAQS. Areas with a strong likelihood of violating the PM10 NAAQS and requiring substantial SIP revisions include the Owens Valley area in California. The EPA has placed the Mono Lake area in group III: an area with a strong likelihood of attaining the PM10 NAAQS and therefore probably has an adequate control strategy. See 52 Fed.Reg. 29383.
Nothing in the Clean Air Act suggests Congress intended to rely for enforcement of this Act upon a federal common law remedy. To the contrary, the statute provides the EPA and the states with the power to remedy unlawful air pollution. See 42 U.S.C. §§ 7413, 7420 (federal enforcement procedures) and 7416 (retention of state authority). The Clean Air Act also authorizes citizens to enforce the Act. However, no such enforcement action is brought here.
The Clean Air Act does not “restrict any right which any person may have under any statute or common law to seek enforcement of any emission standard or limitation.” 42 U.S.C. § 7604. In a federal common law nuisance action, the court is asked to determine whether an act or omission causes damage to the public. However, the Act empowers the EPA, not the federal courts, to identify pollutants and concentration levels that endanger or are likely to endanger the health and welfare of the public and requires states to develop a plan for implementing, maintaining and enforcing the NAAQS. 42 U.S.C. § 7410.
Since Congress has not authorized the courts to develop a substantive law of air pollution, if federal common law can be fashioned at all, it will be because a federal rule of decision is “necessary to protect uniquely federal interests.” Texas Industries, 451 U.S. at 640, 101 S.Ct. at 2067. Not all federal interests fall into this restricted category. Rather, a “uniquely federal interest” exists “only in such narrow areas as those concerned with the rights and obligations of the United States, interstate and international disputes implicating the conflicting rights of states or our relations with foreign nations, and admiralty cases.” Id. at 641, 101 S.Ct. at 2067. For purposes of our discussion, the only applicable areas for consideration are whether rights and obligations of the United States are involved or whether there is an interstate dispute implicating the conflicting rights of states. “In these instances, our federal system does not permit the controversy to be resolved under state law, either because the authority and duties of the United States as sovereign are intimately involved or because the interstate ... nature of the controversy makes it inappropriate for state law to control.” Id.
(a) Rights and obligations of the United States.
Appellants argue that there is a significant federal interest in the quality of the air in the Mono Lake area. The district *1415court’s decision also might be read as implicating unique rights and obligations of the United States, when it states that the defendant’s actions “invade federally protected interests ... (the integrity of the nation’s air and water)....”
We acknowledge that in the context of an interstate water pollution case, the Supreme Court stated that federal courts do fashion federal laws where federal rights are involved and that there is a federal common law when dealing with air and water in their ambient or interstate aspects. Milwaukee I, 406 U.S. at 103, 92 S.Ct. at 1392. The Supreme Court made this statement in the following context. The remedy sought by Illinois for interstate water pollution was not within the precise scope of remedies prescribed by Congress in the Federal Water Pollution Control Act. Id. at 103, 92 S.Ct. at 1392. “The Act makes pollution of interstate and navigable waters subject ‘to abatement’ when it ‘endangers the health and welfare of any persons.’ ” Id. at 102, 92 S.Ct. at 1392. The abatement authorized by the Act, however, is a “long-drawn-out procedure.” Id. at 103, 92 S.Ct. at 1392. According to the Supreme Court, “remedies which Congress provides are not necessarily the only federal remedies available” and “[i]t is not uncommon for federal courts to fashion federal law where federal rights are concerned.” Id. at 103, 92 S.Ct. at 1392 (quoting Textile Workers v. Lincoln Mills, 353 U.S. 448, 456-57, 77 S.Ct. 912, 917-18, 1 L.Ed.2d 972 (1957)). Accordingly, in Milwaukee I, the Supreme Court acknowledged a federal common law remedy to abate interstate or navigable water pollution but says nothing regarding federal common law as to the rural fugitive dust at issue here.
By promulgating the Clean Air Act, Congress has recognized “some” limited federal interest with regard to the nation’s air quality. The Clean Air Act also provides that “[e]ach state shall have the primary responsibility for assuring air quality within the entire geographic area comprising such state,” 42 U.S.C. § 7407(a), and “[t]hat the prevention and control of air pollution at its source is the primary responsibility of states and local governments.” Id. at § 7401(a)(3). Thus, there is not “a uniquely federal interest” in protecting the quality of the nation’s air. Rather, the primary responsibility for maintaining the air quality rests on the states.
Additionally, the cases cited in the Texas Industries decision as well as controlling precedent in federal common law nuisance cases indicate that this case does not involve the kind of “right or obligation” that must be protected by federal common law.
In Texas Industries, 451 U.S. at 641, n. 12, 101 S.Ct. at 2067, n. 12, the Court cited United States v. Little Lake Misere Land Co., 412 U.S. 580, 93 S.Ct. 2389, 37 L.Ed.2d 187 (1973), and Clearfield Trust Co. v. United States, 318 U.S. 363, 63 S.Ct. 573, 87 L.Ed. 838 (1943), as examples of cases in which “rights and obligations of the United States” were involved.
The Little Lake Misere case involved a written agreement made by the United States to acquire land for public purposes explicitly authorized by Congress. The Supreme Court held that “in a setting in which the rights of the United States are at issue in a contract to which the United States is a party and ‘the issue’s outcome bears some relationship to a federal program, no rule may be applied which would not be wholly in accord with that program.’” Id., 412 U.S. at 604, 93 S.Ct. at 2403 (citation omitted). In Clearfield Trust Co., the United States was suing for reimbursement on a forged check drawn on the Treasurer of the United States. The Court held that “the rule of Erie R.R. Co. v. Tompkins, 304 U.S. 64, 58 S.Ct. 817, 82 L.Ed. 1188, does not apply and the rights and duties of the United States on commercial paper which the United States issues are governed by federal rather than local law.” 318 U.S. at 366, 63 S.Ct. at 574-75. The specific facts underlying the Little Lake Misere and Clearfield Trust cases clearly indicated that the federal rights (U.S. agreement to acquire land) and obligations (U.S. commercial paper) at issue required application of federal law. The controversies intimately involved “the authority and duties of the United States as sovereign,” Texas Industries, 451 U.S. at *1416641, 101 S.Ct. at 2067, therefore making application of anything but federal law inappropriate.
The facts of our case stand in marked contrast. Although there might arguably be some unquantified federal interest in protecting the nation’s air quality, this type of interest does not necessarily involve the authority and duties of the United States as sovereign to the extent that our federal system requires that the controversy be resolved under federal law, to the exclusion of state law.
Quite to the contrary, application of state law in this case is particularly appropriate. The appellant has failed to demonstrate that “our federal system does not permit the controversy to be resolved under state law,” Texas Industries, 451 U.S. at 641, 101 S.Ct. at 2067, nor could it do so. There is no conflict between the alleged federal policies or interests that might be involved in this case and the use of California’s common law of nuisance. Additionally, because the appellant is currently seeking the protection of California nuisance laws in California State court, the appellant has clearly demonstrated that California nuisance law is both well-suited and applicable to the case at bar. Therefore, it is inconsistent to argue “that both federal and state nuisance law apply to this case. If state law can be applied, there is no need for federal common law; if federal common law exists, it is because state law cannot be used.” Milwaukee v. Illinois, 451 U.S. at 313, n. 7, 101 S.Ct. at 1790, n. 7. Finally, we note that California may have a substantial interest in applying its own nuisance laws to this case which involves primarily state law claims. See Little Lake Misere, 412 U.S. at 599, 93 S.Ct. at 2400; Wallis v. Pan American Petroleum Corporation, 384 U.S. at 68, 86 S.Ct. at 1304. Consequently, our case does not involve the same sort of rights and obligations of the United States as sovereign which required application of federal law in Little Lake Misere and Clearfield Trust.
Rather, our case is more analogous to the Texas Industries case, where the Court decided that a right to contribution among antitrust wrongdoers did not implicate “uniquely federal interests” of the kind that oblige courts to formulate federal common law. In so holding, the Court reasoned “that contribution among antitrust wrongdoers does not involve the duties of the Federal Government, the distribution of powers in our federal system, or matters necessarily subject to federal control even in the absence of statutory authority.” Texas Industries, 451 U.S. at 642, 101 S.Ct. at 2068. Similarly, because our case also does not involve any of the requisite “uniquely federal interests,” we decline to recognize the appellants’ federal common law nuisance claim based on air pollution.
(b) Interstate Dispute
The district court accepted the allegations that dust storms “pollute not only the air of California but also that of Nevada” (District Court Order at p. 22), and concluded that the plaintiff had stated a federal common law nuisance claim based on air pollution. We disagree.
Assuming that air pollution reaches into Nevada, this case does not involve the kind of interstate dispute previously recognized as requiring resolution under federal law, namely, a controversy whose interstate nature makes “it inappropriate for state law to control.” Texas Industries, 451 U.S. at 641, 101 S.Ct. at 2067.
In Georgia v. Tennessee Copper Company, 206 U.S. 230, 27 S.Ct. 618, 51 L.Ed. 1038 (1907), the State of Georgia sought to enjoin the Tennessee Copper Company from “discharging noxious gas from their works in Tennessee over the plaintiff’s territory.” Id. at 236, 27 S.Ct. at 619. Although the Supreme Court did not explicitly state that it was creating a federal common law nuisance cause of action based on air pollution, the Court did enjoin the copper company’s continued pollution of Georgia’s air. The Court focused on the facts that the plaintiff was a state and the injury was interstate, rather than domestic, in nature: “[i]t is a fair and reasonable demand on the part of a sovereign that the air over its territory should not be polluted on a great scale ... and whatever domestic destruction [the forests] have suffered, should not be further destroyed or threatened by acts of persons beyond its control. ...” Id. at 238, 27 S.Ct. at 619.
*1417In Milwaukee I, supra, the Court recognized a federal common law action for water pollution caused by Wisconsin sewerage commissions polluting Lake Michigan. Again, the case centered on an interstate controversy which involved a state suing sources outside its domain which were causing pollution within the state. The Court concluded that: “[f]ederal common law and not the varying common law of the individual states, is, we think, entitled and necessary to be recognized as a basis for dealing in a uniform standard with the environmental rights of a state against improper impairment by sources outside its domain.” Id., 406 U.S. at 107, n. 9, 92 S.Ct. at 1395, n. 9, quoting Texas v. Pankey, 441 F.2d 236, 241-42 (10th Cir.1971).
The great similarity between these cases underscores the limited context in which the Court has been willing to recognize a federal common law nuisance claim based on air pollution due to an interstate dispute. It appears that the Court considers only those interstate controversies which involve a state suing sources outside of its own territory because they are causing pollution within the state to be inappropriate for state law to control, and therefore subject to resolution according to federal common law.
Therefore, true interstate disputes require application of federal common law. See Milwaukee I, 406 U.S. at 107, n. 9, 92 S.Ct. at 1395, n. 9; Georgia v. Tennessee Copper, 206 U.S. at 237, 27 S.Ct. at 619; Missouri v. Illinois, 200 U.S. at 520, 521, 26 S.Ct. at 269, 270. Because we conclude this is essentially a domestic dispute and therefore not the sort of interstate controversy which makes application of state law inappropriate, reliance on federal common law is unnecessary. Audubon cannot rely on the federal common law of nuisance to state its air pollution claim.
Although we recognize that this ease could develop into a dispute involving conflicting rights of States, that is not the case before this court, and we do not decide legal questions based on contingencies, speculation or potential conflicts. See Reserve Mining Co. v. Environmental Protection Agency, 514 F.2d 492, 520-21 (8th Cir.1975) (en banc); Committee for Consideration of Jones Falls Sewage System v. Train, 539 F.2d 1006, 1008 (4th Cir.1976) (en banc). Because we conclude that Audubon cannot properly assert a federal common law nuisance action based on air pollution on these facts, we need not decide whether or not such a cause of action would be preempted by the Clean Air Act, or whether Audubon would have standing to assert this claim.
B. Remand of the Pendent State Claims
Audubon has appealed the district court’s decision to remand its state claims to state court. Audubon argues that the district court abused its discretion in remanding these claims.
Generally, remand orders are not considered final orders reviewable by appeal. Thermtron Products, Inc. v. Hermansdorfer, 423 U.S. 336, 352-53, 96 S.Ct. 584, 593-94, 46 L.Ed.2d 542 (1976); 28 U.S. C. § 1291 (1987). However, in this case the district judge certified his decision and, therefore, 28 U.S.C. § 1292 (1987) permits this court to review the remand order.
The district court remanded this action to state court after the original basis for removal was deleted in an amendment intended to defeat federal jurisdiction. In Carnegie-Mellon University v. Cohill, — U.S. -, 108 S.Ct. 614, 98 L.Ed.2d 720 (1988), the Supreme Court held that “the pendent jurisdiction doctrine supports giving a district court discretion to remand when the exercise of pendent jurisdiction is inappropriate.” Id. at 619. While it is not clear whether we review such a remand order under the abuse of discretion standard or the clearly erroneous standard, see Survival Systems Division of the Whittaker Corp. v. United States District Court, 825 F.2d 1416, 1419, n. 2 (9th Cir.1987), cert. denied, — U.S. -, 108 S.Ct. 774, 98 L.Ed.2d 861 (1988), we affirm the district court’s decision to remand because it satisfies both standards.
The district judge remanded the state claims to state court because he thought the state judiciary was better suited to decide the state law issues. As the district court stated:
“Because this court believes that the parties are entitled to the more ‘sure-footed *1418reading of applicable law’ (United Mine Workers v. Gibbs, 383 U.S. 715, 726 [86 S.Ct. 1130, 1139, 16 L.Ed.2d 218] (1966)) that a state court can render on state law, I believe a severing of the pendent claims from the federal common law claim and remand of the state claim is appropriate ... state law, especially in an area as critical to the state’s well-being as in the instant case, is better left to the state judiciary.” (District Court Order at p. 35).
Although the federal court has made a substantial commitment of judicial resources to the state claims up to this point in the litigation, this is just one factor the court had the discretion to consider in making its decision to remand. Considering the strong state interest in deciding these complex state law issues identified by the district court, we uphold the district court’s remand order.
Ill
CONCLUSION
Appellees’ federal common law nuisance claim based on water pollution is preempted by the FWPCA and we affirm the district court in that holding. Additionally, we decline to recognize the federal common law nuisance claim based on air pollution because this case does not involve either the rights and obligations of the United States as sovereign, or an interstate dispute making application of state law inappropriate. Accordingly, we reverse the district court’s holding that Audubon could state a federal common law nuisance claim for air pollution and therefore we need not decide whether the air pollution claim was preempted by the Clean Air Act. Finally, we have jurisdiction to review this remand order and uphold the district court’s decision to remand the state claims to state court. Accordingly, we vacate the judgment and remand to the district court for its remand of the entire case to the state court.
AFFIRMED IN PART, VACATED AND REMANDED.