An unjust law is no law at all
An unjust law is no law at all, in Latin lex iniusta non est lex, is an expression of natural law, acknowledging that authority is not legitimate unless it is good and right. It has become a standard legal maxim around the world. History. Throughout history, philosophical and religious writers have often objected to unjust laws. For example, in Isaiah 10: In the fourth century AD, Augustine of Hippo said "for I think a law that is not just, is not actually a law" (""nam mihi lex esse non videtur, quae justa  non fuerit""). He wrote this when discussing why evil exists. His conclusion was that it's ultimately a problem caused by people departing from good or just behavior. Should laws be obeyed? Yes, but only if they are just. Thomas Aquinas exhaustively examines the legitimacy of man-made laws and whether they should be obeyed, in Summa Theologica. He asks "do man-made laws have to be obeyed?" His answer is no; a law only need to be obeyed if it is legitimate in three ways: Aquinas says that the disobedience should not itself cause harm or lead people into  evil. He refers to Isaiah establishing that it is always lawful to avoid oppression. In Civil Disobedience, Henry David Thoreau also called into question the legitimacy of any law that was unjust. He says: Martin Luther King Jr, in Letter from Birmingham Jail, referred to both Augustine and Aquinas, saying that Jim Crow laws were unjust and should be eschewed, in establishing his rationale for the goodness of civil disobedience. India. In Indian philosophy, the idea that a rule is not a true law unless just is based on the idea of Rita, a possible cognate for "right" in English . This natural law foundation establishes rules for what is a "law" or "truth", a form of order so high that even the gods themselves must obey or be in the wrong. They do not govern Ṛita, but manifest it through their ordinances and retributions, their rewards and punishments. They don't "govern" it; they serve it as agents and ministers. This view is strongly associated with natural law theorists, including John Finnis and Lon Fuller.