451 U.S. 304 (1981)
The petitioners are the City of Milwaukee, the Sewerage Commission of the City of Milwaukee, and the Metropolitan Sewerage Commission of the County of Milwaukee.1 These municipal corporations operate sewer systems and two sewage treatment plants on the shores of Lake Michigan in Wisconsin, serving an area of approximately 420 square miles with a population exceeding one million.2
The sewer systems are of both the separated and combined variety. On occasion, particularly after a spell of wet weather, overflows occur in the system which result in the discharge of sewage directly into Lake Michigan or tributaries leading into Lake Michigan.
Respondent Illinois complains that these discharges, as well as the inadequate treatment of sewage at the two treatment plants, constitute a threat to the health of its citizens. Pathogens, disease-causing viruses and bacteria, are allegedly discharged into the lake with the overflows and inadequately treated sewage and then transported by lake currents to Illinois waters. Illinois also alleges that nutrients in the sewage accelerate the eutrophication, or aging, of the lake.3 Respondent Michigan intervened on this issue only.4
Illinois' claim was first brought to this Court when Illinois sought leave to file a complaint under our original jurisdiction. Illinois v. Milwaukee, supra. We declined to exercise original jurisdiction because the dispute was not between two States, and Illinois had available an action in federal district court.5 On May 19, 1972, Illinois filed a complaint in the United States District Court for the Northern District of Illinois, seeking abatement, under federal common law, of the public nuisance petitioners were allegedly creating by their discharges.6
Five months later Congress, recognizing that the Federal water pollution control program has been inadequate in every vital aspect, passed the Federal Water Pollution Control Act Amendments of 1972, Pub. L. 92-500, 86 Stat. 816.7 The Amendments established a new system of regulation under which it is illegal for anyone to discharge pollutants into the Nation's waters except pursuant to a permit.8 Petitioners operated their sewer systems and discharged effluent under permits issued by the Wisconsin Department of Natural Resources (DNR), which had duly qualified under § 402 (b) of the Act, 33 U. S. C. § 1342 (b) (1976 ed. and Supp. III), as a permit-granting agency under the superintendence of the EPA.9 Petitioners did not fully comply with the requirements of the permits and, as contemplated by the Act, § 402 (b) (7), 33 U. S. C. § 1342 (b) (7), see Wis. Stat. Ann. § 147.29 (West 1974), the state agency brought an enforcement action in state court. On May 25, 1977, the state court entered a judgment requiring discharges from the treatment plants to meet the effluent limitations set forth in the permits and establishing a detailed timetable for the completion of planning and additional construction to control sewage overflows.10
Trial on Illinois' claim commenced on January 11, 1977. On July 29 the District Court rendered a decision finding that respondents had proved the existence of a nuisance under federal common law, both in the discharge of inadequately treated sewage from petitioners' plants and in the discharge of untreated sewage from sewer overflows. The court ordered petitioners to eliminate all overflows and to achieve specified effluent limitations on treated sewage. A judgment order entered on November 15 specified a construction timetable for the completion of detention facilities to eliminate overflows. Separated sewer overflows are to be completely eliminated by 1986; combined sewer overflows by 1989.11 On appeal, the Court of Appeals for the Seventh Circuit affirmed in part and reversed in part. 599 F. 2d 151. The court ruled that the 1972 Amendments had not pre-empted the federal common law of nuisance, but that in applying the federal common law of nuisance in a water pollution case, a court should not ignore the Act but should look to its policies and principles for guidance. The court reversed the District Court insofar as the effluent limitations it imposed on treated sewage were more stringent than those in the permits and applicable EPA regulations. The order to eliminate all overflows, however, and the construction schedule designed to achieve this goal, were upheld.12 We granted certiorari to consider the effect of this legislation on the previously recognized cause of action. 445 U. S. 926.13
Whether the Federal Water Pollution Control Act Amendments of 1972 displaced the federal common law cause of action for abatement of a public nuisance caused by interstate water pollution?14
When Congress addresses a question previously governed by federal common law the need for such an unusual exercise of law-making by federal courts disappears.15 Federal common law is subject to the paramount authority of Congress and is a necessary expedient only in the absence of an applicable Act of Congress.16 The appropriate analysis is whether the legislative scheme spoke directly to the question not whether Congress affirmatively proscribed the use of federal common law.17
Yes. The 1972 Amendments established a comprehensive regulatory program for water pollution occupying the field through permits and effluent limitations supervised by an expert agency.18 The Act's permit system directly addresses the discharges from petitioners plants and overflows as evidenced by the Wisconsin DNR permits and the 1977 state court judgment.19 The comprehensive nature of the program described by Congress as a total restructuring leaves no room for federal common law remedies in this area.20
The 1972 Amendments displaced the federal common law cause of action.21
Related opinions on this issue
Joined by Marshall And Stevens, Jj.
Justice Blackmun dissented arguing that the Act preserved federal common law through section 505(e) which preserves rights under any statute or common law.22 He maintained that Congress intended no such extinction of the federal common-law remedy approved in Illinois v. Milwaukee.23 The dissent emphasized that the language and structure of the Act support preservation of the federal common law of nuisance.24
The EPA's own reliance on it supports this view.25 The unique role of federal common law in resolving interstate disputes required a more thorough exploration of congressional intent before concluding displacement.26
Whether federal courts may impose effluent limitations on discharges from sewage treatment plants that are more stringent than those incorporated in permits issued under the Act?27
Federal courts lack authority to impose more stringent effluent limitations under federal common law than those imposed by the agency charged by Congress with administering the comprehensive scheme.28
No. The permits issued to petitioners incorporated specific effluent limitations from EPA regulations.29 The district court's order imposed stricter limits but the Act thoroughly addresses effluent limitations through the administrative scheme.30 The Court of Appeals erred in stating that federal courts could require more stringent limitations under federal common law.31
Federal courts may not impose more stringent effluent limitations.32
Whether the Act's permit and enforcement scheme for overflows from combined and separated sewer systems leaves any room for federal common law remedies?33
No. The permits explicitly address overflows requiring plans for elimination or control monitoring and reporting.3637 The state enforcement action resulted in a judgment with timetables for correction.38 There is no interstice to be filled by federal common law as the regulatory regime established by the Act has addressed the overflows.39
The scheme leaves no room for federal common law remedies.40