While we're looking at the first Magna Carta (written in 1215), that was really only version 1.0.
There are many similarities, and some glaring differences, in the later editions. For example: it turns out that King John wasn't the only monarch to be a bit offended by that whole "twenty-five angry barons get to pillage the king's house" clause.
After 1225 they stopped rewriting the thing and it hasn't changed since, but they keep releasing it. In fact, it's one of the oldest bestsellers around.
While nothing could possibly replace the Magna Carta's place in our hearts, the English Bill of Rights eventually replaced the Magna Carta in English law.
It turns out that in four hundred years some things had changed…and a medieval code of laws wasn't really cutting it anymore in the courtroom. (Maybe it was the fact that the serfs had been freed, or that the parliament now had more power than the monarchy.)
But even with the changes to better fit modern times there are still tons of carry-overs from that old piece of parchment that gave the world the idea that rights could be listed in the first place. (Source)
Let's face it: the average American colonist was going to worship any scrap of paper that took power away from a king.
The Magna Carta was like their holy grail. It didn't really matter that a lot of the clauses didn't really apply to their situation, they were just totally stoked to not be the first people ever to think that the King of England was a loon who should be stopped from making important decisions and operating heavy machinery.
And yeah, some of the basic ideas from the Magna Carta did make their way into the Constitution, like simply the fact that governments should have some stuff written down beforehand that says what their leaders can and can't do.
Even more than the U.S. Constitution, the legacy of the Magna Carta can be seen in the Bill of Rights. Beyond the fact that they're both organized in handy list-form, some of the Magna Carta's clauses are eerily similar to those in the Bill of Rights, specifically the amendments about due process of trial and the rights of the accused.
Like the rebel barons of the 1200s, the American colonists were sick and tired of the sloppy way that the Brits conducted (or didn't conduct) court trials. Also that part about the king not taking forests and rivers from himself sounds kind of like the Third Amendment, where the government is forbidden from taking whatever they want to house soldiers.
Basically both documents are all about boundaries…and how the British had been disrespecting them for forever.
He's probably not someone you've ever heard of, because when textbooks start listing great philosophers and thinkers he doesn't often make the cut.
But that's unfair and here's why: he made the Magna Carta relevant hundreds of years after it had been written. In fact, he's why you're learning about it right now. He took an ancient, medieval text and said, "Listen up, people, this old thing is chock full of good ideas that we need to put into our government right away."
Lawyers win cases if they can cite precedents and Sir Coke was the first to drag out the ultimate precedent (the Magna Carta) and slap everyone around with it. (Source)
Wouldn't it be great if the Magna Carta were applied to all people everywhere? In case you live in a country that hasn't written a bill of rights or a constitution inspired by the Magna Carta, the UN has your back, because the Great Charter inspired their charter.
There are some big differences—the UN Charter is firmly based in the modern world and attempting to cover a lot more ground—but it still would never have been possible if those barons hadn't gotten the ball rolling back in Runnymede. (Source)