The Magna Carta was a charter issued in 1215 that placed limitations on King John's power and established the relationship between the king and his subjects. It reduced the king's authority and paved the way for the establishment of parliament. The barons forced King John to agree to the Magna Carta after growing unhappy with his high taxes, unsuccessful wars, and quarrels with the church. The Magna Carta established principles of constitutional law such as habeas corpus and due process that still influence legal systems today.