The writ of habeas corpus is a cornerstone of Western law, often called "The Great Writ." Habeas corpus in Latin literally means "produce the body," and the writ requires the Government to justify its imprisonment of someone. It's often used by prisoners to challenge the conditions of their confinement or their underlying convictions on grounds not reviewable on direct appeal (in fact, most of the death-row "appeals" you hear about are actually habeas proceedings).
It's also been used by people detained by the Government in the War on Terror at places like Guantanamo Bay. Which is why South Carolina GOP Senator Lindsay Graham last week introduced an amendment to a bill that would strip Gitmo detainees of the right to challenge their confinement, essentially overruling the Supreme Court's decision on the issue last summer. Why, you might ask, is it so important to allow these terrorists to have access to the civilian courts? Because, as attorney P. Sabin Willet points out in today's Washington Post, sometimes the Government gets it wrong:
Adel [Willet's client] is innocent. I don't mean he claims to be. I mean the military says so. It held a secret tribunal and ruled that he is not al Qaeda, not Taliban, not a terrorist. The whole thing was a mistake: The Pentagon paid $5,000 to a bounty hunter, and it got taken
Nevertheless, he continues to be held by the Government. This kind of thing should not happen in a country that values the rule of law and respect for human rights. And if Graham's amendment goes through, you can be sure the United States will no longer be one of those countries.