Suppose that the United States captures a high-level al-Qaeda leader who knows the location of a weapon of mass destruction in an American city. Sen. John McCain's amendment would prevent the president from taking necessary measures--short of torture--to elicit its location.

To protect the United States against another 9/11-style attack, it makes little sense to deprive ourselves of important, and legal, means to detect and prevent terrorist attacks. Physical and mental abuse is clearly illegal. But should we also take off the table interrogation methods that fall short of torture--such as isolation, physical labor, or plea bargains--but go beyond mere questioning?

While the impulse behind the McCain amendment is worthy, it would not have prevented the abuses at Iraq's Abu Ghraib prison, which were unrelated to interrogations. Those abuses resulted from sadistic behavior on the "night shift" and were illegal. The Geneva Conventions--which already prohibit the torture or cruel, inhumane or degrading treatment of prisoners--clearly apply in Iraq.

McCain's only real effect would be to limit the interrogation of al-Qaeda terrorists. They are not prisoners of war under Geneva, but a stateless network of religious extremists who do not obey the laws of war, who hide among peaceful populations, and who seek to launch surprise attacks on civilian targets. They have no armed forces to attack, no territory to defend, and no fear of killing themselves in their attacks.

Information is the primary weapon in this new conflict. Intelligence gathered from captured operatives may present the most effective means of stopping terrorist attacks. We should not deprive our military and intelligence agencies of the flexibility to prevent another attack, one perhaps using weapons of mass destruction, on an American city by a terrible and unprecedented enemy.

John Yoo is a visiting scholar at AEI.