President Bush's proposal to try foreign terrorist suspects in a secret military court is justified by the magnitude of the Sept. 11 attacks and the continued threat of more violence, the White House said Wednesday.
Bush approved use of the secret court in cases involving terror assaults. His emergency order does not require approval from Congress.
"This is a new tool to use against terrorism," White House Counsel Albert Gonzales said.
The executive order applies only to people who are not U.S. citizens.
Lawyers said that a special military court would be able to try accused terrorists in greater secrecy and much more quickly than a conventional court can. Such tribunals haven't been seen in this country since World War II.
In the sort of court proposed, the government would have more freedom with evidence and statements it introduces into trial, according to David B. Rivkin, a Washington lawyer who published a legal paper on Bush's options this month.
Rivkin said a military court could use items of proof that would probably be excluded from a regular criminal case, and jurors would also be more likely to support a death sentence.
Convicted terrorists might be executed shortly after a trial, with few or none of the long delays for additional appeals that are common in criminal courts, lawyers said.
"The easy way [for the government] to go is a military commission," former military prosecutor A. Jeff Ifrah said.
Unlike U.S. district courts or military courts martial, "a commission is governed by whatever the president and to a certain extent the Congress dictate," Ifrah added.
Military commissions date to the late 17th century, operating side by side with the better-known courts martials. The United States last convened one on orders from President Franklin D. Roosevelt, after German saboteurs secretly landed on U.S. shores in 1942.
Detention and trial of accused terrorists by a military tribunal is necessary "to protect the United States and its citizens, and for the effective conduct of military operations and prevention of terrorist attacks," Bush's five-page order said.
The administration also could hold a trial in an ordinary criminal court, but said it wanted the option of using a military court.
In either a military or a civilian court, any suspect would retain rights to a lawyer and to a trial by jury, the administration said.
"These are extraordinary times and the president wants to have as many options as possible," said Mindy Tucker, a spokeswoman for the Justice Department. "This option does not preclude any Department of Justice options that might also be available."
Bush's order sets out many of the rules for a future military tribunal. A senior Justice Department official, speaking on condition of anonymity, said only noncitizens would be tried before the commission.
The defense secretary would follow up with more specifics should a tribunal be needed, the White House said.
Anyone ever held for trial before such a court would certainly challenge its legitimacy, said Eugene Fidell, president of the National Institute of Military Justice in Washington, and a lawyer who regularly practices before military courts.
"This is going to raise a raft of legal issues and will be a test of the president's power," Fidell said.
Gonzales, the president's top lawyer, said a military commission could preserve the secrecy of U.S. investigations into terror networks.
In a conventional court, a victory might require giving other terrorists information about U.S. "sources and methods," Gonzales said. "We don't want to have to do that."
A military trial also could be held overseas, and Gonzales said prosecutors may feel a trial in America would be unsafe.
Recent terrorism trials have taken place under heavy security in U.S. criminal courts, where the rules require the government to reveal its evidence either in open court or in filings it must fight to keep secret.
Laura W. Murphy, director of the Washington office of the American Civil Liberties Union, said for a military trial to have constitutional legitimacy, Bush must justify why ordinary courts could not do the job.
"Absent such a compelling justification, today's order is deeply disturbing and further evidence that the administration is totally unwilling to abide by the checks and balances that are so central to our democracy," she said.
Roosevelt had the World War II saboteurs secretly tried by military commission, and six were executed. The Supreme Court upheld the proceeding, although Rivkin said it is not clear whether that case would guide a modern challenge. An enemy who sneaked onto U.S. soil "for the purposes of waging war by destruction of life or property" was a combatant who could be tried in a military court, the Supreme Court ruled then.
Military tribunals also were used during and after the Civil War.
The Associated Press contributed to this report.