[SpyGuy]

They can be impeached by Congress, but that seems to require official malfeasance (fraud, bribe-taking, etc.).

I would argue that they are continually committing official malfeasance (fraud).

[Leatherneck_MT]

I would have to argue that impeachment is only one of 2 ways of getting rid of them. However the 2nd option is too terrible to even think of.. at this time.

[B Knotts]

Well, it's kind of interesting. Impeachment is defined as requiring high crimes or misdemeanors, however...that definition specifically applies to the president and vice-president.

The legitimate causes for impeachment of judges is not actually defined.

Article III, Section 1 states that:

The judicial power of the United States, shall be vested in one Supreme Court, and in such inferior courts as the Congress may from time to time ordain and establish. The judges, both of the supreme and inferior courts, shall hold their offices during good behaviour, and shall, at stated times, receive for their services, a compensation, which shall not be diminished during their continuance in office.

So, really it could boil down to the interpretation of the phrase "good behaviour."