What does the constitution say about Billl of attainer?

The U.S. Constitution explicitly prohibits bills of attainder in Article I, Sections 9 and 10. A bill of attainder is a legislative act that singles out and punishes an individual or group without a trial. This prohibition is intended to protect individuals from arbitrary punishment by the government and ensures that legal proceedings include due process. Thus, both federal and state legislatures are barred from enacting such laws.