Fr. Williams Saunders. “Does the Church Condone Tyrannicide?”. Herald Columnist. September 27th, 2001 – “Tyrannicide has had support from various philosophers and theologians through the centuries, including the ancient Greeks and Romans, most notably Cicero; Catholics, most notably John of Salisbury (d. 1180) Jean Petit (d. 1411), and Suarez (d. 1617); and Protestants, most notably, Luther, Melanchthon, Zwingli, and Calvin.
St. Thomas Aquinas gave the most substantial argument for tyrannicide. He based his position on his arguments for just war and capital punishment. St. Thomas concluded, “He who kills a tyrant (i.e. an usurper) to free his country is praised and rewarded” (In 2 Sentences, 44.2.2).”