A constitutionally prohibited law that inflicts punishment without a judicial trial.

(n) An action made by the legislature which announces an identified person as guilty of an offense, predominantly in the case of treason. Article I, Section 9 of the U.S. Constitution forbids such bills.

“Legislative acts, no matter what their form, that apply either to named individuals or to easily ascertainable members of a group in such a way as to inflict punishment on them without a judicial trial are bills of attainder prohibited by the Constitution.” United States v. Brown, 381 U.S. 437, 448-49 (1965).