Civil rights and, more broadly, human rights are sets of moral principles or norms that describe standards of human behavior. Civil rights allow for individuals to freely participate in and criticize the state. Human rights as moral principles, and then later as codified rules and laws, have been around since the dawn of civilization. As the idea of nation-states has become refined, so too have the laws that govern them, including human rights laws. Although amendments to the Constitution after the Civil War guaranteed equal rights to all Americans, many US citizens—especially African Americans—still experienced discrimination and segregation on a wide scale. Civil rights legislation and policy promulgated since the civil rights movement is ordered around the idea of "protected classes" or characteristics. Arguably the most influential civil rights law since the end of the civil war is the Civil Rights Act of 1964.