Wrong. Read Saenz v. Roe.
When a state law treats residents differently, that falls under 14th amendment Due Process or Equal Protection. When California attempted to amend it's AFDC program to treat new residents differently, it was struck down under Equal Protection in Green v. Anderson, 811 F. Supp. 516, 521.
When Congress enacted PRWORA, it authorized a state to treat new residents differently. Since this was a federal law, it violated not only a state citizen's rights but a United States citizen's rights.
The federal law was struck down as a violation of P&I. That's the way I read it, anyways.