A former President can be impeached. He looses that title and many things that were put into place when they were a sitting Pres. can be undone.
In the 1870s, Ulysses S. Grant’s secretary of war, William Belknap, was impeached on charges of corruption and bribery. Belknap resigned before the House could vote to impeach him, but the House went ahead and impeached him anyway.
