The Magna Carta, signed in 1215, established the key principle that the monarchy is subject to the law, thus beginning to define individual rights against arbitrary power. It introduced concepts such as due process and the idea that no one, including the king, is above the law. This was revolutionary in promoting the idea that individuals have certain rights that cannot be infringed upon without legal justification. The Magna Carta set a precedent for future legal documents, influencing constitutional development in England and later shaping legal systems in many democratic nations, emphasizing the importance of individual freedoms and limiting governmental power.