What was the purpose of the Magna Carta?

The Magna Carta, referred to as the Great Charter of English liberty, granted under considerable duress by King John at Runnymede on June 15, 1215.  This declaration of law required the King to proclaim certain rights of free men, respect certain legal procedures, and accept that his will could be bound by the law. It explicitly protected certain rights of the King’s subjects and implicitly supported what became the “writ of habeas corpus” allowing the appeal against unlawful imprisonment for the first time in English law.  The Magna Carta was arguably the most significant early influence on the extensive historical process that led to the rule of constitutional law in the English speaking world of today.

The Magna Carta actually influenced the development of the common law and many constitutional documents, including the United States Constitution, in aspect as which the Magna Carta declares that:

“No free man shall be taken, imprisoned,…or in any other way destroyed…except by the lawful judgment of his peers, or by the law of the land. To no one will we sell, to none will we deny or delay, right or justice.”

History has acknowledged some relationship that American law and constitutionalism had to the Magna Carta and English common law, however, as close as Magna Carta and American concepts of liberty are, they remain distinct. The Magna Carta is a charter of ancient liberties guaranteed by a king to his subjects; the Constitution of the United States is the establishment of a government by and for the people.

Read more here.