The problems began with George W. Bush’s decision, in January, 2002, to send purported terrorism suspects to Guantánamo. Some were tortured at the base; some were tortured in other locations, such as the C.I.A.’s “black sites.” Close to eight hundred people passed through the prison. Their paths there were disparate. Some were associated with Al Qaeda or other terrorist groups. Others were detained based on flimsy or false evidence, in some cases as a result of local feuds. Twenty-two were migrant Uyghurs; several were children under the age of sixteen. The inhumane carelessness with which all the prisoners were treated was visible to the world, and it damaged America’s reputation. Successive Administrations attempted to rationalize the legal disorder of those years by setting up quasi-judicial procedures that ultimately crippled attempts to apply due process and render justice.

Early on, the Bush Administration decided that if prisoners at Guantánamo were ever tried it would be not in civilian courts but before newly designed “military commissions.” That scheme ran into trouble with the Supreme Court, which ruled that key elements of it were unconstitutional. In 2009, Eric Holder, Barack Obama’s first Attorney General, announced that K.S.M. and his four alleged co-conspirators would instead be charged in federal court in lower Manhattan, near the scene of the crime. An eighty-one-page indictment against the men was handed down by a grand jury in the Southern District. Republicans, and some Democrats, treated this development not as a triumph but as an outrage. Holder backed down, and the Obama Administration began proceedings under a revamped military-commission law. At about the same time, Congress passed a provision in the National Defense Authorization Act blocking all funds that might be used to move prisoners to the United States—even to stand trial or to serve a sentence. That provision has been renewed every year since.

Looking back, there was something supremely weird about the furor that greeted the idea that accused mass murderers might be prosecuted in U.S. courts—that’s what the courts are for. It can be partly explained by the politics of fear in the period after 9/11. There was a notion that military commissions would be quick and efficient. Also, it was widely recognized that detainees at Guantánamo had been tortured. A real trial—a fair trial—would lay that bare. Guantánamo was seen as a place to hide the government’s crimes. In that sense, shame was a factor as well.

But it turned out that building a novel commission system was not expedient at all; some of the time-consuming hearings in the 9/11 case have involved litigation, rife with untested appellate issues, over basic matters such as the rules of evidence and lawyers’ access to their clients. Federal courts, by contrast, have proved very effective in prosecuting terrorists, and have an extensive record of dealing with classified matters. And, just as evidence elicited under torture is not admissible in civilian courts, it is not supposed to be admissible in military commissions, either. (Nor should it, for reasons of reliability, legality, and morality.) Obama had pledged to close Guantánamo; instead, he worked at the margins, sending lower-profile prisoners to other countries, whittling down their numbers. Donald Trump stopped doing even that. There are currently thirty-nine prisoners at the base (including the 9/11 defendants); the majority have been held for more than a decade without any charges being filed against them. Meanwhile, the military-commission proceedings slog on.

Until Congress stops renewing the ban on transferring detainees to this country, the most effective thing that the Biden Administration can do to bring the 9/11 trial to a quicker, more just conclusion is to take the death penalty off the table. This is within its power to accomplish. The pursuit of the death penalty is another reason the trial is taking so long; as in civilian courts, additional procedures must be followed in capital cases. For example, the fact that the men had been tortured could be introduced as a mitigating factor at the sentencing stage. Some of the pretrial hearings have been about attempts by the defense to preserve evidence of torture for that purpose, which the government has resisted. Dropping the death penalty would return the focus to the nearly three thousand people who were killed on 9/11 and reduce the likelihood that Biden will leave an unfinished trial for an unknown future President. Doing so could also make it easier to strike plea deals—a guilty plea for life in prison.

A plea deal might seem like a tepid ending to what had once been envisioned as the trial of the century. And it would not close Guantánamo, though it would help. Karen J. Greenberg, the director of the Center on National Security at Fordham Law, and the author of “Subtle Tools,” a new book on laws and norms after 9/11, said last week that Biden’s best chance of finally finishing that job would be to move aggressively to make sure that every remaining prisoner is charged with a crime or else transferred to another country. Some of the cases have been regarded as too murky to resolve with either of these actions, but after almost two decades it’s time to make those hard calls. Our legal forever war must also come to an end. ♦