WASHINGTON, July 12, 2025 (BSS/AFP) - A US appeals court on Friday scrapped 9/11 mastermind Khalid Sheikh Mohammed's plea agreement that would have taken the death penalty off the table and helped conclude the long-running legal saga surrounding his case.

The agreement had sparked anger among some relatives of victims of the 2001 attacks, and then-US defense secretary Lloyd Austin moved to cancel it last year, saying that both they and the American public deserved to see the defendants stand trial.

Austin "acted within the bounds of his legal authority, and we decline to second-guess his judgment," judges Patricia Millett and Neomi Rao wrote.

Plea deals with Mohammed as well as two alleged accomplices -- Walid bin Attash and Mustafa al-Hawsawi -- were announced in late July last year.

The decision appeared to have moved their cases toward resolution after years of being bogged down in pre-trial maneuverings while the defendants remained held at the Guantanamo Bay military base in Cuba.

But Austin withdrew the agreements two days after they were announced, saying the decision should be up to him, given its significance.

He subsequently said that "the families of the victims, our service members and the American public deserve the opportunity to see military commission trials carried out in this case."

A military judge ruled in November that the deals were valid and binding, but the government appealed that decision.

The appeals court judges on Friday vacated "the military judge's order of November 6, 2024, preventing the secretary of defense's withdrawal from the pretrial agreements."

And they prohibited the military judge "from conducting hearings in which respondents would enter guilty pleas or take any other action pursuant to the withdrawn pretrial agreements."

Much of the legal jousting surrounding the 9/11 defendants' cases has focused on whether they could be tried fairly after having undergone torture at the hands of the CIA -- a thorny issue that the plea agreements would have avoided.

Mohammed was regarded as one of Al-Qaeda chief Osama bin Laden's most trusted lieutenants before his March 2003 capture in Pakistan. He then spent three years in secret CIA prisons before arriving at Guantanamo in 2006.

The trained engineer -- who has said he masterminded the 9/11 attacks "from A to Z" -- was involved in a string of major plots against the United States, where he attended university.

The United States used Guantanamo, an isolated naval base, to hold militants captured during the "War on Terror" that followed the September 11 attacks in a bid to keep the defendants from claiming rights under US law.

The facility held roughly 800 prisoners at its peak, but they have since slowly been sent to other countries. A small fraction of that number remain.