Hines v. Davidowitz (1941)
From Federalism in America
In Hines v. Davidowitz (1941), the U.S. Supreme Court invalidated a Pennsylvania law requiring aliens to register with state authorities because the federal Alien Registration Act of 1940, which required aliens to register with federal authorities, had preempted the field. While the federal law did not explicitly preclude state regulation, the Court held that preemption was implied because of the paramount federal interest in the regulation of resident aliens.
Robert W. Langran
SEE ALSO: Pennsylvania v. Nelson; Preemption