As a sovereign, Arizona has the inherent power to exclude persons from its territory. ~ Antonin ScaliaScalia in his dissent to the Supreme Court overturning the Arizona immigration law has devised from whole cloth a new constitutional provision that the individual states may expel entire classes of people from their borders.
While he does not state this specifically, the logical extension of his opinion is that the individual states have the sovereign power to exclude homosexuals or Mexicans. Oregon can pass a law forbidding entry to Californians. Texas can expel Jews, if it wishes. Scalia would revive a shitload of 19th century anti-Chinese laws.
The word "exclude" appears only once in the Constitution where it excludes from the Census untaxed Indians. At no point does the Constitution grant a "power to exclude" to the states. Scalia has to reference an 18th century Swiss diplomat to find such a power and even there the power is only available to nation-states and not provinces within a nation.
Scalia makes the insane case that Arizona, and every other state, may have its own immigration policy.