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The first prisoner to leave Guantanamo since President Trump took office was supposed to be on his way today. Instead, all 41 of the Guantanamo inmates Trump inherited remain there, including five others who had previously been cleared for release. NPR's David Welna explains.

DAVID WELNA, BYLINE: The legally binding deal to release confessed al-Qaida operative Ahmed al-Darbi today could not be more clear, says his lawyer, City University of New York law professor Ramzi Kassem. In exchange for pleading guilty to war crimes four years ago and being a witness for the prosecution of two other Guantanamo inmates, Kassem says, Darbi was supposed to serve out the remaining nine years of his sentence in his native Saudi Arabia.

RAMZI KASSEM: The agreement between my client and the U.S. government provides for his transfer to Saudi custody by no later than February 20, 2018. That's today's date.

SARAH HIGGINS: Mr. Darbi's transfer from Guantanamo detention to Saudi Arabia, it's not going to take place today.

WELNA: That's Commander Sarah Higgins, the Pentagon spokeswoman for detainee policy. She says it's not the fault of the U.S. that Darbi did not leave Guantanamo today as expected.

HIGGINS: We're looking to get him transferred, but we're awaiting assurances from the Saudi Arabian government to move forward on his departure. The Department of Defense hopes this transfer will take place soon.

WELNA: If Darbi does not leave Guantanamo, says defense lawyer Kassem, there won't be much incentive for other inmates to turn state witness in the war court known as military commissions.

KASSEM: Frankly, it would make little sense for the U.S. government to renege on a deal with my client after describing his testimony as, quote, "unprecedented" in counterterrorism prosecutions to date. That would virtually guarantee that no one else would cooperate with the U.S. government and its military commissions.

WELNA: Meanwhile, five other detainees remain in Guantanamo even though members of half a dozen federal agencies had cleared them for release before Trump took office. Chicago lawyer Tom Durkin represents one of them.

TOM DURKIN: Our client is stranded there because there's no procedures from the Department of Defense to secure the release.

WELNA: The last administration's special envoy who arranged prisoner transfers at the Pentagon has not been replaced. Attorney Shelby Sullivan-Bemis (ph) also represents Guantanamo captives who've been cleared for release. She says nothing's happening.

SHELBY SULLIVAN-BENNIS: In speaking to embassies of my clients who are cleared, the response is, well, I'm not sure where to go because our country desk doesn't have anyone to speak to. You know, no one answers the phone. There is no office. What can we do? There's nothing to do.

WELNA: The U.S. State Department also once had its own special envoy for Guantanamo.

LEE WOLOSKY: That used to be my office. And my office now really functionally does not exist.

WELNA: That's Lee Wolosky. He was the Obama administration's last State Department official charged with finding countries to receive Guantanamo captives whose continued imprisonment was judged no longer necessary.

WOLOSKY: My job was to move them out after six agencies and departments of the United States government unanimously concluded that a particular individual no longer needed to be in Guantanamo. And there's no indication that this administration is doing anything to move them out of Guantanamo.

WELNA: Rear Admiral Edward Cashman is in charge of the troops holding Guantanamo's 41 prisoners. He says eligible prisoners are still getting regular reviews of their status.

REAR ADM EDWARD CASHMAN: There is a process in place, the periodic review process, to make a determination regarding whether or not those detainees represent a continuing threat to U.S. military personnel, U.S. forces, operations, allies, civilians.

WELNA: Still, 11 prisoners are now suing the U.S. government. Their lawyers say they've been jailed for up to 16 years in Guantanamo with no due process. Even those who've been told they can leave, they say, now have no way out. David Welna, NPR News, Washington.

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