Impeachment has been in the news lately. In this 9-0 decision from 1993, the U.S. Supreme Court makes it clear that impeachment by the House of Representatives and trial by the Senate are purely political processes. There is no judicial review of either process. If a federal official is impeached and subsequently removed from office, there is no appeal to any court. Congress has sole authority. The judiciary has none.
The case itself:
"Impeachment Inquiry Transcript of Proceedings"
