42 U.S.C. § 1983
42 U.S.C. § 1983, popularly known as "Section 1983," is a federal law that allows lawsuits for violations of constitutional rights.
Section 1983 establishes a cause of action for any person who has been deprived of rights secured by the Constitution or laws of the United States by a person acting under color of state law. A plaintiff must prove that (1) that the conduct was committed by a person acting under color of state law and (2) that as a result of this conduct plaintiff was deprived of rights, privileges or immunities secured by the Constitution or the laws of the United States.
The first requirement is known as the state action requirement. Plaintiff must prove that conduct was "fairly attributable to the state," and attribution is limited because it "preserves an area of individual freedom by limiting the reach of federal law and federal judicial powers." Lugar v. Edmondson Oil Co., Inc., 457 U.S. 922, 936 (1982).
In Monell v. Department of Social Services, the U.S. Supreme Court held that municipalities and local governments can be sued if the action was attributable to an official policy. They do not enjoy absolute immunity. But the defendant municipal officials must have had "final policymaking authority" to bind the municipality.
The Eleventh Amendment prohibits Section 1983 claims against states and therefore state officials.