MAGNA CARTA, on which King John placed his seal 800 years ago today, is synonymous in the English-speaking world with fundamental rights and the rule of law. It’s been celebrated, and appropriated, by everyone from Tea Party members to Jay Z, who called his latest album “Magna Carta Holy Grail.” 

But its fame rests on several myths. First, it wasn’t effective. In fact, it was a failure. John was a weak king who had squandered the royal fortune on a fruitless war with France. Continually raising taxes to pay for his European adventures, he provoked a revolt by his barons, who forced him to sign the charter. But John repudiated the document immediately, and the barons sought to replace him. John avoided that fate by dying.

The next year, his young son reissued Magna Carta, without some of the clauses. It was reissued several times more in the 13th century — the 1297 version is the one on display in the National Archives and embodied in English law. But the original version hardly constrained the monarch.

A second myth is that it was the first document of its type. Writing in 1908, Woodrow Wilson called it the beginning of constitutional government. But in fact, it was only one of many documents from the period, in England and elsewhere, codifying limitations on government power.

A third myth is that the document was a ringing endorsement of liberty. Even a cursory reading reveals a number of oddities. One clause prevents Jews from charging interest on a debt held by an underage heir. Another limits women’s ability to bear witness to certain homicides. A third requires the removal of fish traps from the Thames.