The system works if and only if the SCOTUS rules strictly according to the Constitution and applicable laws. That's why Kagan's idiotic nonsense corrupts the court and undermines the very foundations of the federal government.
In theory, justices can be impeached for "high crimes and misdemeanors" through the House of Representatives and the Senate. In practice, being an idiot and a political hack doesn't rise to that level. That's a shame, but it is what it is.