What is the Bill of Attainder?

A Bill of attainder is a legislative act that allows a person or group of people to be charged with a crime and allows the government to punish the person or people without offering them the benefit of a trial. It is used for very serious situations where someone is believed to be guilty of a grievous crime, such as treason. It has been used by some countries, but is banned in the U.S. by the Constitution.