If so, by whom, and under what circumstances? What are the consequences? Would a federal judge with a lifetime appointment lose it as a consequence?
Assuming that the judge is an attorney licensed to practice in the state of Washington, he can be disbarred by the state supreme court. The rules are here. The grounds are statutorily specified in RCW 2.48.220, which could be a misdemeanor involving moral turpitude, or willful disobedience of a court order, or other things. There is no requirement that a federal judge be licensed to practice law in some state, so the consequence of disbarrment would be that he could no longer work as an attorney in that state. Part of the US Court code of conduct for US judges, Canon 4, says that
A judge should not practice law and should not serve as a family member’s lawyer in any forum. A judge may, however, act pro se and may, without compensation, give legal advice to and draft or review documents for a member of the judge’s family.
So taking away his ability to practice law would not make a huge difference.