A federal judge this morning blocked enforcement of the most controversial components of Arizona’s SB 1070 immigration law, just one day before the law was to go into effect.

SB 1070 has been the target of considerable student protest and organizing nationally since it was passed this spring, and is expected to be a flash point for activism when students return to campus in the fall.

Judge Susan Bolton found a “substantial likelihood” that legal residents would be subject to wrongful arrest under the law, and ruled that the statute would thus “impose a ‘distinct, unusual and extraordinary’ burden on legal resident aliens that only the federal government has the authority to impose.”

Update | Here’s the text of the judge’s order.