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 introduced concepts such as due process and the idea that the monarch's powers could be limited, forming a foundation for modern constitutional law. The Magna Carta was a response to King John’s heavy-handed rule and served as a catalyst for the development of parliamentary democracy and individual rights. Its enduring influence can be seen in various legal frameworks, including the United States Constitution and the Universal Declaration of Human Rights.