Iwas busy mapping out a column urging Congress to help the Bush administration prevent terrorist mass murders by giving it new investigative and detention powers—a proposal likely to horrify civil libertarians. Then I heard that the administration might be on the verge of making a claim that would horrify me: that it already has near-dictatorial powers to lock up suspected terrorists, under the "law of war," without meaningful judicial review.

This raises a question for those in Congress who see our current legal restraints on the investigation and detention of suspected terrorists as sacred and immutable. Which would be worse: To relax those restraints by making it easier to search, wiretap, interrogate, and detain suspected terrorists subject to carefully drafted congressional protections against error and abuse? Or to watch passively as the administration bypasses civilian law entirely by invoking ever-broader wartime emergency powers to do whatever it wants?

The cases of two U.S. citizens now in military detention—including the man arrested in Chicago on suspicion of plotting a radiological "dirty bomb" attack—have sharpened the dilemma. According to my sources (whom I hope are mistaken), administration lawyers are preparing to argue that the military has virtually unlimited power to detain, virtually incommunicado, for as long as the president chooses, not only these two but also you, me, the Muslim cleric down the street, and anybody else whom the president declares to be an "enemy combatant." In this view, the courts have no power to order a detainee to be released even if the detainee has compelling evidence that his arrest was a terrible mistake.

If that is the administration's position—and it would be consistent with its so-far sketchy statements about the military detentions of Abdullah al-Muhajir (aka Jose Padilla), the Brooklyn-born suspected dirty-bomb plotter; and Yasser Esam Hamdi, another U.S. citizen—the courts should reject it. But they should also recognize that presidential decisions on military matters are entitled to great deference. And the availability of the military-power option paradoxically reinforces the need for Congress to make the president's other option—the civilian justice system—more amenable to preventing terrorism.

The first reason to adopt new legislation is that, as I argued in my June 8 column, the current legal restraints on the government's investigative powers are unduly stringent, and are partly responsible both for our failure to prevent the September 11 hijackers and for our unnecessarily great vulnerability to future attacks. The second reason is that such legislation may be the only way to prevent the administration from drifting into ever-more-sweeping use of military power on American soil, perhaps including warrantless military searches, wiretaps, spying, and detentions.

It's not hard to see why the military-detention approach appeals to administration officials who are more concerned about preventing terrorist attacks than about legal niceties. A case like al-Muhajir's presents a devilishly difficult legal dilemma: As long as the Constitution is not a suicide pact, the government should not have to release people likely to be planning terrorist mass murders. But it will often have good reasons to avoid bringing criminal charges in the civilian courts, or at all. In the al-Muhajir case, for example, the administration either lacked proof of any crime (he was arrested before he had done much) or could not disclose its evidence without compromising vital intelligence secrets. That left no plausible basis in civilian law for keeping him locked up. So it made perfect sense to invoke the president's military-law power to detain enemy combatants.

On the other hand, as long as this is a free country, the president should not be able to snatch people off the streets and subject them to the functional equivalent of martial law. The prospect of error or abuse may seem remote in the case of

al-Muhajir. But over the long haul, the government is more likely to make mistakes about the intentions of U.S. citizens picked up in this country than about soldiers captured on foreign battlefields. And history shows that detentions without due process have often been used to suppress legitimate domestic dissent.

Would the Supreme Court uphold a claim of presidential power to detain suspected enemy combatants without meaningful judicial review? Two World War II precedents suggest that the commander in chief's powers under the law of war are very broad—but not necessarily unlimited. The detainees in those cases did not deny that they were enemy combatants. And today's Supreme Court might well—and should—rule that detainees who do deny this are entitled to some kind of hearing on whether the president is mistaken.

The best solution might be a streamlined administrative process at the Pentagon—including a right to counsel and to call witnesses—for deciding whether there are reasonable grounds for finding that an individual detainee is an enemy combatant, while at the same time protecting the confidentiality of any intelligence sources and methods. Federal courts should be able to review and overturn decisions ordering detention only if they are manifestly unsupported by the administrative record. The government should have a right of expedited appeal. The goal would be to provide some protection against error or abuse without opening the door to undue judicial meddling in military decisions.

Congress and the administration should work out such a review process and write it into law. And while they are at it, they should also loosen the civilian-law restraints on the government's powers to investigate and detain suspected terrorists. (The provisions suggested below were too controversial to make it into the largely incremental USA-Patriot Act enacted last October.) These provisions could be made to apply only to noncitizens, which would make the law more politically palatable and more likely to survive judicial review. But the dangers come from U.S. citizens, too.

This nation faces an unprecedented internal security threat from a foreign-based mass movement of fanatical terrorists whose goals include murdering as many Americans as they can and using weapons of mass destruction as soon as they can get them. Their modus operandi is to infiltrate and blend into our society until they are ready to strike. Some of them are U.S. citizens, as are some terrorists who are unconnected with Al Qaeda. The best hope for preventing these people from murdering countless Americans is to investigate suspects, and to detain some of them, before the government has evidence clearly implicating them in any crime or terrorist plot.

A key provision could allow the attorney general to order a physical search, wiretap, or other electronic surveillance by certifying that he or she has personally reviewed evidence establishing reasonable grounds to believe that the proposed action would prevent a terrorist attack and thus save one or more lives. The new statute could also provide for the arrest and detention for up to 30 days of any person certified by the attorney general to be reasonably suspected of terrorist intent; and aggressive interrogation of such detained suspects, based on a broad interpretation of the doctrine of New York v. Quarles, a 1984 Supreme Court decision that created a "public safety" exception to Miranda v. Arizona and related cases.

As a safeguard against abuse and excessive use of these extraordinary powers, the new law should specify that any evidence obtained through its provisions may not be used in any legal proceeding other than a prosecution for crimes involving terrorism. And to avoid unnecessary impositions upon detainees—many and perhaps most of whom may prove not to be terrorists—those not charged with any crime should be housed in comfortable, motel-like quarters, away from convicts and criminal defendants. The detainees should be treated with respect and courtesy, restrained only so much as necessary to prevent escapes and violent attacks; and they should be paid, say, $500 in compensation for each day of detention, plus reimbursement of any documented lost wages or other economic losses.

Some of these new powers would require modifications to Supreme Court case law. But Congress should not be shy about seeking such modifications. They are necessary to prevent terrorist attacks. They would be confined to terrorism cases, and they would be consistent with the intentionally flexible language of the relevant constitutional provisions. The Fourth Amendment requires only that searches (including wiretaps) and seizures (including arrests) be "reasonable." The Fifth Amendment does not limit aggressive interrogation per se, but rather use of "compelled" statements "in any criminal case." The Sixth Amendment right to counsel similarly applies only "in ... criminal prosecutions."

If these proposals nonetheless offend your sense of civil liberties—as they might once have offended mine—consider the likely alternative: creeping martial law.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.