KILLING HABEAS CORPUS.

President Abraham Lincoln suspended habeas corpus in Maryland on April 27, 1861, two weeks after the Confederate attack on the Union garrison at Fort Sumter. "Lincoln could look out his window at the White House and see Robert E. Lee's plantation in Virginia," Akhil Reed Amar, a professor at Yale Law School and the author of "America's Constitution," said. "He was also facing a rebellion of so-called Peace Democrats in Maryland, meaning there was a real chance that Washington would be surrounded and a real threat that the White House would be captured." On Lincoln's order, federal troops arrested Baltimore's mayor and chief of police, as well as several members of the Maryland legislature, who were jailed so that they couldn't vote to secede from the Union.

Since the Middle Ages, habeas corpus--"You should have the body"--has been the principal means in Anglo-American jurisprudence by which prisoners can challenge their incarceration. In habeas-corpus proceedings, the government is required to bring a prisoner--the body--before a judge and provide a legal rationale for his continued imprisonment. The concept was so well established at the time of the founding of the American Republic that the framers of the Constitution allowed suspensions of the right only under narrow circumstances. Article I, Section 9, states, "The Privilege of the Writ of Habeas Corpus shall not be suspended, unless when in Cases of Rebellion or Invasion the public Safety may require it." Such suspensions have been rare in American history. The most recent occasion was in 1871, when President Ulysses S. Grant sent federal troops to South Carolina to stop attacks by the Ku Klux Klan against newly emancipated black citizens. This fall, however, Congress passed, and President Bush signed, a new law banning the four hundred and thirty detainees held at the American naval base at Guantanamo Bay, and other enemy combatants, from filing writs of habeas corpus.

The law, known as the Military Commissions Act of 2006, was a logical culmination of an era of one-party rule in Washington. During the Presidency of George W. Bush, the executive branch, with the eager acquiescence of its Republican allies in Congress, has essentially dared the courts to defend the rights of the suspected Al Qaeda terrorists, who have been held at Guantanamo, some for as long as four years. The Supreme Court has twice taken up that challenge and forced the Administration to change tactics; the new law represented a final attempt to remove the detainees from the purview of the Court. Now, of course, Republicans no longer control Congress, but the change in the law of habeas corpus may be permanent.

Arlen Specter was an unlikely steward of the demise of habeas corpus. The Pennsylvania Republican, a senator since 1980, has long been known as a moderate in his caucus, one of the few remaining in a party that has shifted sharply to the right during his career. (The Wednesday Lunch Club, a group of liberal and moderate Republican senators, once had a dozen members. Now, after the defeat in this month's election of Senator Lincoln Chafee, of Rhode Island, it will have three: Specter and the two senators from Maine, Olympia Snowe and Susan Collins.) Moreover, for all his years as a legislator, Specter remains by temperament a litigator and an iconoclast. In his autobiography, "Passion for Truth" (2000), he writes with pride about his work as a young investigator for the Warren Commission; as a crusading Philadelphia district attorney; and as an aggressive cross-examiner of Anita Hill in Clarence Thomas's Supreme Court confirmation hearings. He has, he wrote, a "fetish for facts," and faith in proceedings like habeas corpus to protect individual rights.

Yet it was Specter who, as chairman of the Judiciary Committee, after leading the fight to preserve habeas corpus, at the last moment voted for the Administration's plan restricting it. At seventy-six, Specter, having survived several bouts of life-threatening illness, has lost some of the abrasiveness that earned him the nickname Snarlin' Arlen, but he generally says what he means, even when it might give offense. His self-confidence sometimes verges on arrogance; his most common expression is a knowing smirk. (It is evident in the cover photograph of his autobiography.) With some justification, and with typical bravado, Specter asserts that the debate over habeas corpus could have been avoided, if only his Republican colleagues had listened to him.

Shortly after September 11, 2001, and the American invasion of Afghanistan, Specter proposed that Congress develop a set of rules for handling the prisoners--the so-called "enemy combatants"--who were captured there. Along with Richard J. Durbin, the Illinois Democrat, Specter introduced the Military Commission Procedures Act of 2002, which would have established a system of trials for the alleged Al Qaeda detainees, with defendants guaranteed, among other things, the presumption of innocence and the right to ...