U.S. District Court Judge Stephen Locher issued a preliminary injunction because he said the U.S. Department of Justice and civil rights groups who filed suit against the state were likely to succeed in their argument that federal immigration law preempted the law approved this spring by Iowa lawmakers. He stopped enforcement of the law “pending further proceedings.”

“As a matter of politics, the new legislation might be defensible,” Locher wrote in his decision. “As a matter of constitutional law, it is not.”