The central issue of Arizona's tough and controversial new immigration law is the role state and local authorities can play in confronting those who cross the border illegally. The fate of the law hinges on whether federal law trumps state law. "If I were betting, I think the (Supreme Court) will strike down SB0170 at the same time that it allows some room for discretion at the state level," said Peter Spiro, who teaches immigration law at Temple's Beasley School of Law.