The Supreme Court on Monday refused to hear an appeal from Khalid Sheikh Mohammed and two other accused September 11 plotters, rejecting their last-ditch bid to force the government to honor a plea deal it tore up more than two years ago. The order removes one of the final legal obstacles standing between the self-described architect of the 2001 attacks and a military commission trial where he could again face execution.

Mohammed, Mustafa al-Hawsawi and Walid bin Attash have been held at Guantanamo Bay since 2006. In 2024, after two years of negotiation, they struck a plea agreement with military prosecutors — approved by a military commission judge and the Pentagon's senior Guantanamo official — that would have taken the death penalty off the table in exchange for guilty pleas and life sentences without parole.

Days later, then-Defense Secretary Lloyd Austin revoked the deal after it drew fierce criticism from Republican lawmakers who argued the men responsible for killing nearly 3,000 people should not be spared execution. Military courts initially sided with the defendants, ruling Austin lacked the authority to unilaterally cancel an agreement his own department's officials had signed off on.

A split appeals court, then silence from the high court

That set up a fight at the U.S. Court of Appeals for the D.C. Circuit, which ruled 2-1 last year that Austin had acted within his legal authority. Judges Patricia Millett and Neomi Rao formed the majority; Judge Robert Wilkins dissented, arguing his colleagues should have deferred to the military courts' own reading of military rules. Attorneys for bin Attash said at the time they were weighing a further appeal — the one the Supreme Court declined to take up this week.

THE MEN ARE ACCUSED OF ORCHESTRATING THE DEADLIEST TERROR ATTACK ON U.S. SOIL — BUT A TRIAL HAS TAKEN MORE THAN TWO DECADES TO REACH A COURTROOM

The case's long road reflects years of pretrial fighting over evidence obtained through CIA torture of the defendants in secret overseas prisons after their capture, questions that have dogged the prosecution since Mohammed's arraignment. A fourth man originally charged alongside the three, Ali Abdul Aziz Ali, was not party to this week's appeal.

With the plea-deal path now foreclosed, prosecutors and defense lawyers are headed toward a military commission trial at Guantanamo tentatively set for 2028, where Mohammed, al-Hawsawi and bin Attash would once again face the possibility of a death sentence if convicted. Pretrial hearings — already among the longest-running in American legal history — are expected to resume in the coming months as both sides prepare for a case that has outlasted four presidential administrations.