The Second Circuit Court of Appeals has ruled that New York City must implement and enforce four transportation control strategies contained in the New York air quality implementation plan.¹ In a citizens suit brought by several environmental groups and individuals under §304 of the Clean Air Act seeking enforcement of the plan, the court held that the city was precluded from raising constitutional defenses based on the Tenth Amendment as recently construed by the Supreme Court in National League of Cities v. Usery² because it had failed to raise such objections to the Environmental Protection Agency's (EPA) 1973 approval of the plan in a petition for review of that approval within the 30-day period allowed by §307(b)(2).³ The court also distinguished Brown v. EPA⁴ and several other decisions⁵ which struck down, because of constitutional considerations, EPA's program of forcing state and local governments to implement transportation controls and in which appeals are now awaiting decision before the Supreme Court. Here, the court emphasized, the city and the state developed and consented to the measures contained in the implementation plan, and judicially ordered enforcement will not substantially usurp integral local governmental functions.