The federal district court for the northern district of California has for the second time in two years upheld the constitutionality of state and local ordinances enacted to control noise around municipal airports in the face of claims that the restrictions illegally invade a field of regulation preempted by the federal government. The cases are noteworthy because they suggest that the seemingly broad federal preemption of aircraft noise regulation announced by Justice Douglas in City of Burbank v. Lockheed Air Terminal,¹ may in reality be quite narrow. The district court's latest ruling, in National Aviation v. City of Hayward,² involved a challenge by four commercial airline operators to an ordinance prohibiting aircraft operations producing noise levels above 75 decibels (on the A scale) between 11:00 p.m. and 7:00 a.m., a restriction very similar to the one invalidated in Burbank. The court held that the Hayward ordinance was constitutional, however, after concluding that it was a valid exercise of the municipality's proprietary powers as owner and operator of the airport in question.

The doctrine of preemption arose in American jurisprudence as a response to the need for nationally uniform regulation over certain activities. Simply stated, the basic principle is that when the federal government validly regulates some activity, the Supremacy Clause of the federal Constitution operates to bar subordinate government entities from also regulating it.³ In order for a court to rule that a particular field of regulation has been preempted, it must find a clear expression of congressional intent to exclude state regulation and that conflicting state regulations would upset the pervasive scheme of federal control.