"Shapiro v. Thompson (1968) considered the constitutionality of a state law that established a one-year residency requirement for welfare recipients. The Court struck down the law, finding it a violation of the "right to travel" (really, more the right to migrate). The Court said it had "no reason to ascribe the source to any particular constitutional provision," relying instead on the "fundamental rights" prong of equal protection analysis. In a subsequent case, the Court upheld residency requirement for in-state tuition benefits. In so doing, the Court distinguished Shapiro, which it said involved access to "basic necessities of life." In Zobel v Williams, the Court, 8 to 1, struck down a Alaska scheme that distributed royalties from the state's mineral revenues to state residents based on the length of state residency. Residents received $50 in benefits for each year they lived in Alaska. Various justices offered three different reasons for invalidating the plan.

Finally, in Saenz, the Court breathed new life into the Citizenship Clause of the Fourteenth Amendment in finding that clause to be violated by a California law that set lower welfare benefits for newer residents than for long-term residents. The Court says the clause "does not allow for degrees of citizenship based on length of residence."

(http://law2.umkc.edu/faculty/projects/ftrials/conlaw/newresi...)