By MICHAEL B. MUKASEY

The terrorism alert issued this week to Americans traveling abroad, and the events that generated it, have put in bold relief yet again dilemmas we face—some self-created—in our ongoing struggle with militant Islamists.

On the surface, the news certainly is not all bad. A German citizen of Afghan descent captured in Afghanistan disclosed a plot to American interrogators at the Bagram Air Field prison. The plan, Ahmed Sidiqi said, was to conduct coordinated attacks on tourists in European cities, and it involved other naturalized German citizens from Afghanistan. U.S. authorities issued a terrorism alert to travelers, and on Monday five of the conspirators, along with three Pakistanis and three others of undisclosed nationality, were killed in a drone strike in North Waziristan.

So far so good. One captured terrorist in military custody since July—at a location that prevents him, at least for the moment, from hauling his captors into a U.S. court—discloses valuable intelligence that appears to have headed off, at least for the moment, an atrocity.

Below the surface, the news is more troubling. Sidiqi and his associates are German citizens; that, and the arrest of a French citizen of Algerian origin as a suspected member of al Qaeda (plus 11 other arrests in southern France), make it plain that Islamist terrorists are succeeding in recruiting people whose passports give them free entry into all the countries of the European Union, and facilitate their travel in general. In 2009 and 2010 alone some 43 American citizens or residents of various backgrounds have been arrested here and abroad for terrorist-related activity, according to the Bipartisan Policy Center’s National Security Preparedness Group.

Further, Sidiqi and those of his colleagues killed in the drone strike were recruited at the Taiba mosque in Hamburg, the same mosque attended by Mohammed Atta, the lead plotter among the 9/11 hijackers. And this group was said to have been planning simultaneous attacks of the sort carried out in November 2008 in Mumbai by Lashkar-e-Taiba, a terrorist group based in Pakistan.

Two items are worthy of note. First, the simultaneous attacks: This was a characteristic not only of 9/11 and the attacks on U.S. Embassies in Kenya and Tanzania in 1998, but also of the 1995 plot led by Omar Abdel Rahman, the so-called blind sheikh. That conspiracy meant to detonate near-simultaneous bombs at landmarks around New York, including the Holland and Lincoln Tunnels, the George Washington Bridge and the United Nations. In tape-recorded conversations the plotters discussed what they thought would be the especially demoralizing effect on their enemies, and the correspondingly aggrandizing effect on them, of simultaneity.

Second, the Mumbai attack was notable for its ability to rivet the world’s attention for an extended period of time. Terrorists cherish that sort of attention.

All of which is to say that the tourist plot is of a piece with what we have faced, whether we were aware of it, for more than two decades. Are we taking the steps necessary to deal with it?

Here again, the news certainly isn’t all bad. Our intelligence capabilities have been stepped up considerably in recent years, particularly with regard to electronic surveillance. The laws and regulations necessary to allow the government to use the techniques it needs are in place. And the Obama administration, commendably, has said it will seek legislation compelling service providers to have available the means necessary to permit the government to conduct Internet surveillance when authorized by warrant. In addition, guidelines put in force at the end of 2008 have empowered the FBI to gather intelligence domestically using conventional surveillance techniques and human sources.

Yet in other respects we seem stymied. Look no further than this week’s headlines. How do we deal with the people planning simultaneous attacks on tourists—likely to be principally Americans—in Europe?

The government seems to present us only with the choice that we kill them with drones or give them Miranda warnings and access to a 24-karat justice system designed for conventional criminals. There are better ways, including but not limited to military commissions already provided by law but shunned by the administration, or other special- purpose tribunals that can be established by Congress.

Detaining terrorist conspirators for intelligence-gathering purposes—wholly apart from whatever they may be charged with planning or doing—does not appear to be an option for this administration, certainly not if they are apprehended in this country while seeking to detonate a bomb in an airplane over Detroit or in an SUV near Times Square. Those who joined the orgy of self-congratulation after this week’s sentencing of Times Square bomber Faisal Shahzad might, when they sober up, consider what we did not find out about who sent him and who else may be on the way— because Shahzad was valued more as a defendant than as an intelligence source.

We will not always be so fortunate to have our would-be attackers detained by the military at Bagram. And even such detention may be the subject of further litigation if the Supreme Court agrees to review last spring’s appellate decision denying habeas corpus to detainees at Bagram. Yet as recently as World War II this country held tens of thousands of war prisoners here and abroad without a single one of them being allowed to require his custodians to answer to a U.S. court.

For us, today, the lesson is clear. The importance of being able to gather human intelligence has never been more starkly demonstrated than in the capture and questioning of Ahmed Sidiqi, and the resulting drone attack. The former director of the CIA, Gen. Michael V. Hayden, has likened trying to survive on electronic intelligence alone to trying to put together a jigsaw puzzle without looking at the picture on the box. It is human intelligence that provides that picture.

Like Gulliver in the land of the Lilliputians, we seem tied down; unlike Gulliver, we have woven and tied the strings ourselves.

Mr. Mukasey was attorney general of the United States from 2007 to 2009.