A U.S. appeals court on Friday refused to allow Khalid Sheikh Mohammed, the accused mastermind of the September 11, 2001, attacks, and two of his co-defendants to plead guilty under agreements that would have spared them the death penalty.

The ruling by a 2-1 panel of the U.S. Court of Appeals for the District of Columbia Circuit upended an attempt to bring an end to a military prosecution of the three detainees in Guantanamo Bay, Cuba, that has been beset by two decades of legal gridlock.

Those plea agreements had been offered last year and accepted by the official who oversees the Pentagon’s Guantanamo war court, only to be revoked in August by then-Defense Secretary Lloyd Austin after Republican lawmakers attacked the agreements.

A military judge, though, ruled that Austin lacked authority to revoke the plea deals in a decision that was upheld in December by U.S. Court of Military Commission Review. The judge then scheduled prompt plea hearings.

The D.C. Circuit at the behest of former Democratic President Joe Biden’s administration agreed to pause those proceedings while it heard the government’s legal challenge, which Republican President Donald Trump’s administration continued.

U.S. Circuit Judges Patricia Millett and Neomi Rao, writing for the majority, in Friday’s ruling said Austin “indisputably had legal authority to withdraw from the agreements.”

“Having properly assumed the convening authority, the Secretary determined that the ‘families and the American public deserve the opportunity to see military commission trials carried out,” the judges wrote. “The secretary acted within the bounds of his legal authority, and we decline to second-guess his judgment.”

Millett was appointed by Democratic President Barack Obama, while Rao is a Trump appointee. U.S. Circuit Judge Robert Wilkins, an Obama appointee, dissented from what he called a “stunning” ruling, saying his colleagues should have deferred to the decisions of military courts interpreting military rules.

A lawyer for Mohammed and one of his co-defendants, Mustafa Ahmed Adam al Hawsawi, did not respond to requests for comment, nor did the Pentagon.

Matthew Engle, an attorney for the third defendant, Walid Muhammad Salih Mubarak bin ‘Atash, said he was considering a potential further appeal, including to the U.S. Supreme Court.

Mohammed is the most well-known inmate at the detention facility in Guantanamo Bay, which was set up in 2002 by then-U.S. President George W. Bush to house foreign militant suspects following the September 11, 2001, attacks.

Mohammed is accused of masterminding the plot to fly hijacked commercial passenger aircraft into the World Trade Center in New York City and into the Pentagon. The 9/11 attacks killed nearly 3,000 people.

—

(Reporting by Nate Raymond in Boston; additional reporting by Idrees Ali in Washington, editing by Deepa Babington)