The significance of the Magna Carta for modern legal systems lies in its establishment of the principle that everyone, including the king, is subject to the law. Signed in 1215, it introduced fundamental rights and laid the groundwork for constitutional democracy. Key elements, such as the right to a fair trial and protection from unlawful imprisonment, became foundational to contemporary legal systems. The Magna Carta influenced future charters, including the United States Constitution and the Universal Declaration of Human Rights, symbolizing the enduring quest for justice and individual liberties throughout history.