Only 15 federal judges in U.S. history have been impeached by Congress, but just a handful of them were actually removed from their posts — thanks in part to longstanding precedent about what conduct constitutes “high crimes and misdemeanors.

Republican lawmakers have launched several long-shot attempts to impeach judges who have stood in the way of some of the Trump administration's most aggressive actions. Why it matters: There is a longstanding tradition that federal judges should not be impeached due to disagreements with their rulings — a norm endorsed by Chief Justice John Roberts on Tuesday in a rare rebuke of President Trump from the high court.