A “bill of attainder” refers to a legislatively imposed punishment on an identified individual or group of individuals. These are unconstitutional under Article I, sections 9 and 10. One of the chapters in The Odd Clauses is about these clauses, and one of the key cases I discuss is a recent one involving congressional de-funding of ACORN. The Second Circuit held that this was not a bill of attainder, reversing the district court. Now ACORN has petitioned the Supreme Court to take the case. Details and links here, at SCOTUSblog.