Habeas corpus means that any person that has been arrested or detained MUST be brought before a court of law to see if the detention is just and lawful. In our legal tradition it stems from the Magna Carta. There is a discussion of the history of habeas corpus from the BBC here.

“The power of the Executive to cast a man into prison without formulating any charge known to the law, and particularly to deny him the judgement of his peers, is in the highest degree odious and is the foundation of all totalitarian government whether Nazi or Communist.”
Churchill – November 21, 1943

Habeas Corpus, “you should have the body,” guarantees that a person can only be arrested pursuant to the law, and not simply at the will of some despotic governing authority. It is a legal procedure in the form of a writ that demands that a person be brought before a magistrate and charged under due process, or else that he be immediately released. It protects the people by preventing government from making arbitrary arrests.

Habeas corpus was critical to the founders of our nation. They put it in the Constitution, and it enforces the founding principle that this is a government of laws and not of men. Thomas Jefferson was particularly eloquent on the subject:

“The Habeas Corpus secures every man here, alien or citizen, against everything which is not law, whatever shape it may assume.” –Thomas Jefferson to A. H. Rowan, 1798.

“Freedom of the person under the protection of the habeas corpus I deem [one of the] essential principles of our government.” –Thomas Jefferson: 1st Inaugural Address, 1801.

“[The] bill of rights [should provide] clearly and without the aid of sophisms for… the eternal and unremitting force of the habeas corpus laws.” –Thomas Jefferson to James Madison, 1787.

This is what George Bush wants to destroy. And this is what the 3 Senators, McCain, Graham, and Warner, are willing to give away.