One of the most novel enforcement mechanisms devised by the drafters of the Clean Air Act Amendments of 1970 was §304's "citizen suit" provision.¹ This section, variants of which were later incorporated in the Federal Water Pollution Control Act Amendments of 1972² and a number of other federal environmental statutes,³ authorizes any person to commence civil enforcement suits in federal district court. Such suits may be brought against any person (including the United States, its agencies, and any state or local government instrumentality) alleged to be in violation of an emission standard or limitation or a compliance order issued by the EPA Administrator, if EPA has not already commenced a civil enforcement action under §113.⁴ In addition, an action may be brought against the Administrator himself where he is alleged to have failed to perform any non-discretionary duty under the statute. The purpose of the provision was to encourage, as well as to supplement, federal and state efforts at enforcement.⁵

Of the suits brought to date under §304, most have consisted of challenges to alleged abuses of discretion by the Administrator in setting or failing to issue or revise various regulations or emission standards.⁶ The few suits that have been aimed directly at enforcing an "emission standard or limitation" have run into several obstacles, not the least of which is the charge of being premature while administrative implementation of the Act was still at the standard-setting stage.⁷