What in the world is the Magna Carta?

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The Magna Carta is a document that the nobles forced King John to sign. The nobles were tired of King John and all the kings disrespecting them so they did something about it. The Magna Carta consists of rules like if someone want's to put someone in jail they need a witness.
An example of a king disrespecting a noble is: pretend you are a noble and winter is coming and you need wood to keep warm, and you send a servant to get wood. The servant comes back with little wood and you ask him "why did you get little wood?" and the servant answers "there was no wood the king chopped down all your trees for his castle." Wouldn't that make you mad if the king had done that? I know that there are no kings these days, but you never know the feudalism might take a turn in the future.