The Justice Department has denied a request by Zacarias Moussaoui, the only prisoner ever convicted in the United States of having ties to the Sept. 11, 2001, attacks, to serve the remainder of his life sentence in his native France.

Moussaoui had made the application from the supermax prison in Colorado, using a process that is routinely available to foreign nationals held as U.S. prisoners.

Then on Wednesday, two relatives of people killed in the attacks said they were notified by the Justice Department that the request was denied. “Our office appreciates your concerns and comments regarding Zacarias Moussaoui,” the email said. “I am notifying you that Mr. Moussaoui’s application to transfer to France was denied by the United States on July 26, 2024.”

No explanation was offered for the delay in notification. On July 25, a dozen senators led by Marco Rubio and Rick Scott of Florida wrote to President Joe Biden and Attorney General Merrick Garland that “no consideration whatsoever should be given to this convicted terrorist’s preferences for where to serve his sentence.”

Moussaoui, 56, was arrested in Minnesota a month before the hijackings, which killed nearly 3,000 people in New York, at the Pentagon and in Pennsylvania. For a time after Sept. 11, U.S. officials theorized he was the would-be 20th hijacker in the attacks carried out by 19 men, but later dropped that assertion.

In 2005, Moussaoui pleaded guilty to conspiring to kill American citizens in a federal court case in Alexandria, Va. A jury sentenced him the next year to life imprisonment. He is held in solitary confinement at the federal supermax prison in Colorado, with no possibility of release.

An inmate who is denied a transfer “may normally reapply for transfer two years from the date of denial,” according to the federal prison policy. It was not known if Moussaoui had applied previously because the Justice Department declined to discuss the matter, citing department policy.

Nicole Navas Oxman, a Justice Department spokesperson, had, however, suggested the request would not be granted.

“Zacarias Moussaoui is serving a life sentence following conviction for terrorism offenses,” she said. “The Department of Justice plans to enforce this life sentence in U.S. custody.”