Bill of Attainder
A Bill of Attainder is a law, which neither Congress nor the states can enact under the Constitution, that declares a specific person or group of persons (e.g., someone's children) to be guilty of a crime without a trial.
The U.S. Constitution prohibits a Bill of Attainder in Article I, Section 9, Clause 3. The Founding Fathers supported this ban in order to undo England's law of treason, which had been used against colonists. Later, the U.S. Supreme Court enforced this clause under the doctrine of separation of powers: courts, not the legislature, decide guilt.