Presidents have often asserted disputed powers in the name of national security. Abraham Lincoln, citing a necessity to suppress support for the Confederacy, suspended habeas corpus, the right of suspects to challenge charges against them, in the Civil War.

Eighty years later, after the Japanese attack on Pearl Harbor, President Franklin D. Roosevelt ordering the detention of more than 100,000 Japanese and American citizens of Japanese descent.

Historians often cite these two events, and the circumstances under which the two presidents made such swift and divisive assertions of executive power, as most fitting to the current debate over moves made by President Bush in the wake of September 11.

With the Senate Judiciary Committee today opening hearings, "Wartime Executive Power and the NSA's Surveillance Authority," administration backers argue Mr. Bush's actions pale in comparison to those of past wartime presidents.

Critics rip the administration's assertion that the terrorist attacks warranted interrogation techniques beyond limits on torture set by federal law, open-ended detention of suspects without charges and spying on Americans without oversight.

Many scholars, however, are divided on whether the executive has gone too far.

"All wartime presidents expand their powers to some extent. It's sort of a natural inclination under the pressure of war," says John D. Hutson, president of the Franklin Pierce Law Center in New Hampshire and a former judge advocate general of the Navy.

"Whether you think it's a good idea or not that this is an administration that is drawing power very much to the executive, and to some extent that's a zero-sum game, meaning there is only so much power out there and to the extent that he gets it, it's coming from somebody else, some from Congress, some from the courts and some from the people."

Gary J. Schmitt, director of the program on Advanced Strategic Studies at the American Enterprise Institute, says "the Constitution was designed with different institutional capability, and it's no surprise that in times of a national security crisis the institution that's most institutionally capable of handling such will step into the breach."

President Bush appears to have permanently carved his place in the debate by acknowledging that since September 11 he has authorized the National Security Agency to electronically spy on people in the United States communicating with suspected terrorist-linked individuals overseas without warrants from a secret court created by a 1978 federal law to oversee such activities. ...