Mathews v. Diaz
In Mathews v. Diaz, 426 U.S. 67 (1976), the U.S. Supreme Court applied relaxed scrutiny in upholding the validity of a federal statute that conditioned an alien's eligibility for participation in a federal medical insurance program on the satisfaction of a durational residency requirement, but imposed no similar burden on citizens.
The Court emphasized that Congress, as an aspect of its broad power over immigration and naturalization, enjoys rights to distinguish among aliens that are not shared by the States. Id. at 84-87. See also Hampton v. Mow Sun Wong, 426 U.S. 88, 100-101 (1976); De Canas v. Bica, 424 U.S. 351, 358 n. 6 (1976).