Banisadr was not an Islamic cleric, because Ayatollah Khomeini has insistenced that clerics should not run for positions in the government (which he later took back). Banisadr was the last president of Iran to hold the title of acting commander in chief of the military.
Banisadr was impeached on June 22 of 1981 by the Iranian parliament (as hinted by Ayatollah Khomeini) because of his moves against the clerics in power, and most specifically Mohammad Beheshti, the time's head of juridical system. He later flew to France, and still (as of 2004) lives there.