the speech or debate clause immunizes federal legislators from civil or criminal actions based on legislative acts. In tenney v. brandhove (1951) the Supreme Court, relying on the common law immunity of legislators and the speech or debate clause, held legislators to be immune from federal civil suits based on legislative acts. This legislative immunity, however, does not preclude evidence of legislative acts in criminal prosecutions for corruption.
In what may be an expansion of common law legislative immunity, lake country estates, inc. v. tahoe regional planning agency (1979) held that the appointed members of a bistate agency enjoyed legislative immunity from suits for constitutional violations. The Court also suggested that state legislative immunity does not depend on the existence of the speech or debate clause. Lake Country Estates' extension of absolute legislative immunity to un-elected officials may enable many public bodies or officials that promulgate rules of general application to rely on legislative immunity. For example, in Supreme Court of Virginia v. Consumers Union of the United States (1980) the Court concluded that state supreme court justices enjoyed legislative immunity from damages actions based on their promulgation of unconstitutional rules of conduct for the state bar.
Eisenberg, Theodore 1982 Section 1983: Doctrinal Foundations and an Empirical Study. Cornell Law Review 67:492–505.