President Obama's big speech on the future of the war on terrorism yesterday contained a contradiction that threatens to tie his counter-terror policy in rather thick knots. First he said he prefers to capture detainees instead of killing them. Then he recommitted himself to closing the Guantanamo Bay facility that houses those detainees – without offering an alternate prison. Welcome to a paradox.

Obama turned more than a few heads by declaring his "strong preference" for "the detention and prosecution of terrorists" over sending an armed robot to end their lives. It's hard to know what to make of that. The simplest interpretation is that it's a lie. Whatever Obama's preferences are, he has killed exponentially more people than he has detained and prosecuted.

Obama definitely prefers to prosecute terrorism suspects who are Americans inside the United States. But overseas, outside the declared battlefield of Afghanistan, the only major terrorist he detained and tried criminally is the Somali Ahmed Warsame.

But maybe Obama wasn't lying. Maybe he was signaling a shift in policy. As he restricts the drones but doesn't end the overall shadow wars, it follows that detentions become more important to him. In that case, Warsame illustrates the problem that Obama now confronts.

Sometime in the spring of 2011, U.S. naval forces intercepted Warsame in the Gulf of Aden on suspicion of supporting al-Shebab, al-Qaida's affiliate in Somalia. They quickly found they had no place to put him. Warsame wasn't captured in Afghanistan, so the detention facility on the outskirts of Bagram Air Field wasn't an option. Somalia's government was considered incapable of holding him. And the only remaining detention facility for terrorism suspects is Guantanamo Bay, which the Obama administration is desperately trying to close, so they couldn't very well add to its population without causing a scandal.

So they made do. For months, Warsame was held in the brig of the amphibious assault ship USS Boxer. From there he was secretly brought to Manhattan in July 2011, charged with material support to terrorists, and held at the Manhattan Correctional Center along with 830 other inmates while his pre-trial hearings proceeded under gag order. In March, the U.S. attorney for the southern district of New York announced that Warsame had secretly pled guilty in December 2011. All's well that ends well, right?

Not really. The Boxer's brig was an ad-hoc solution, at best. Adm. William McRaven, now the chief of U.S. Special Operations Command, openly testified to Congress in 2011 that it was a work-around for a detention problem that need a permanent fix.

But is there one? There isn't enough evidence in every case of future captures to merit charges in criminal courts. Military commissions are supposed to be for war crimes, which not every terrorist commits. Some national governments are capable of capturing and securely detaining terror suspects; not all of them are, otherwise Warsame would be tried and imprisoned in Somalia. That leaves the military and the CIA with the fateful option of catching, interrogating and releasing detainees. More on that in a second.

In his Thursday speech, Obama spelled out a couple different options for closing Guantanamo. Once again, he'll seek to transfer most of the detainees cleared for release, either to their home countries like Yemen or to third countries for continued detention. He's open to trying detainees before military tribunals at military brigs inside the continental United States – the major new idea in his detentions policy – as well as in civilian courts.

If Obama thinks there's a workable detentions policy in there, he's in for a major challenge. Transfers apply to the current detainee population, not any future one. Not even New York's Mike Bloomberg, a liberal mayor in the greatest Godless city America has to offer, was willing to allow Gitmo detainees to be tried in Manhattan (never mind the fact that Warsame and at least six other terrorists are jailed in his city right now). And if Obama's talking about either military tribunals or indefinite detention inside the United States, then he's not closing Guantanamo at all – he's just moving it.

So these are the choices Obama has boxed himself into on detentions: moving Gitmo to the States and failing to liquidate the problem he seeks to resolve; or trying some terrorism detainees in criminal courts, which won't be available options in every case and will attract the kind of political opposition that has cowed Obama in the past.

There is, however, another choice, one that Obama's speech did not address: get out of the business of long-term detentions. Just stop. Capture someone, interrogate him for his intelligence value, and if there isn't a case to be made against him, let him go sooner rather than later. It's simpler and cheaper, and in surely most cases, won't involve letting legitimately dangerous people go, since if you know them to be dangerous, you'll have ways of trying them. Should someone actually be let go and blow something up, that will be a horrible weakness of this option, but it will also better respect the grown-up realization that perfect security is both impossible and incompatible with a free society.

Who knows if Obama's actually going to do any of this. His typical GOP adversaries on the issue, like Rep. Buck McKeon (R-Calif.) and Sen. John McCain (R-Ariz.), both issued statements expressing their desires to work with Obama to craft a legal architecture for long-term terrorism detentions going forward. Obama has punted on that in the past, because to accept a new legal framework for terrorism detentions is to implicitly grant that the war must last indefinitely, since any such framework uses the law of war as a foundation. That leaves Obama with few acceptable choices, unless he's willing to prove himself way braver on ending detention than he has in the past.

It's so much easier to kill someone with a drone instead. Hey, wait a minute...