Since the legislation is missing whistleblower protection (a fundamental flaw) there is no way Snowden can make any arguments in a U.S. court, at least not until the legislation is fixed. Unconstitutional or not, the law is just broken. It's painfuly obvious, and I can't fathom why fixing it isn't a higher priority (for example, wouldn't politicians who want votes promise to work for such reform now, after the Snowden debacle?)