Today, June 15th, is the anniversary of the signing of Magna Carta. It wasn't the first legal document to limit the power of the English monarchy, but its the one we remember. And it's worth remembering, even though John repudiated it the moment he'd escaped his rebellious barons' clutches. It established rights such as due process and freedom of travel, as well as the founding principle of the Westminister system of Parliamentary government: that there shall be no taxation without the consent of Parliament.
While John repudiated the Charter, his heirs consistently reissued it, and it became firmly established in British law - to the extent that its now looked on as the founding document of "British liberty". Ironically, it has been almost entirely repealed today. Only four clauses from the 1297 version survive in british law, and only a single clause in New Zealand. But it's perhaps the most important one:
NO freeman shall be taken or imprisoned, or be disseised of his freehold, or liberties, or free customs, or be outlawed, or exiled, or any other wise destroyed; nor will we not pass upon him, nor condemn him [or] deal with him but by lawful judgment of his peers, or by the law of the land. We will sell to no man, we will not deny or defer to any man either justice or right.
in the middle of a war on terror which has seen the erosion of human rights around the world, that's something we should all remember.