"Supporters of the law say that even if Congress meant to restrict subsidies to marketplaces created by the state, no one warned state officials that relying on the federal version would deprive their residents of millions of dollars in insurance subsidies.... Late last month, lawyers for 22 states... told the justices they were blindsided by the claim that federal subsidies might be cut off because they failed to establish state marketplaces.'Surprising states with a dramatic hidden consequence' violates a basic principle of fair dealing between Washington and the states, the state lawyers said in the court brief. Congress 'does not hide elephants in mouse holes,' they added, quoting a comment by Justice Antonin Scalia in a previous case."