This great charter of English liberty was granted by King John at Runnymede, June 15, A.D.1215 after the English nobility took up arms after the King and his government began usurping their rights, undermining their liberty and stealing their property. The king was forced to sign this under pain of death. This codified rights that have been required under common law. 
 
"Here is a law which is above the King and which even he must not break. This reaffirmation of a supreme law and its expression in a general charter is the great work of Magna Carta; and this alone justifies the respect in which men have held it" Winston Churchill, 1956.