[ZULU]

I thought a bill of attainder was a law passed which made an action committed prior to the enactment of the law a crime.

[Borges]

That's an Ex Post Facto law. BOA is trial by legislature.

[RKV]

Nope, thats an ex post facto law. A bill of attainder is an act of legislature declaring a person or group of persons guilty of some crime, and punishing them, without benefit of a trial.