Arizona's police chiefs and county sheriffs hoped a U.S. Supreme Court ruling would settle their long-running debate on what role they should play in immigration enforcement. Instead, the decision has left them with more questions than answers. If federal agents decline to pick up immigrants, the state doesn't have any way to force federal authorities to pick them up and will likely have to let them go unless they're suspected of committing a crime that would require them to be brought to jail, said Peter Spiro, a professor at Temple's Beasley School of Law.