Recent court orders slowing down or indefinitely blocking President Donald Trump’s policy blitz have raised the specter that the executive branch might openly flout the federal judiciary and prompted questions about how judges would respond. Any decision by the administration to defy federal courts would immediately implicate profound constitutional questions about separation of powers that have kept each branch of the government in check for centuries. That’s in large part because it would test the power of courts to enforce rulings that are supposed to be the final word. Legal experts say there are few options to force compliance with...