The significance of the Magna Carta, signed in 1215, lies in its establishment of the principle that everyone, including the king, is subject to the law. It was a response to the tyrannical rule of King John and sought to protect the barons' rights. This document laid the groundwork for modern democracy by asserting that the monarch's power should be limited by legal constraints, promoting the idea of due process. Over centuries, the Magna Carta influenced the development of constitutional law, inspiring future democratic movements worldwide.