His transfer brings the number of men held at Guantanamo to 40, which includes five men facing trial by military commission for their alleged roles planning and supporting the September 11, 2001, terrorist attack and another charged with the attack on the USS Cole in October 2000.
Reuters reported in March that al-Darbi's transfer was advancing.
The widely expected transfer of Ahmed Haza al-Darbi, who pleaded guilty to helping plan a 2002 attack on a French oil tanker, was announced on Wednesday and reduced the notorious jail's population to 40. Sarah Higgins said. "This policy provides our warfighters guidance on nominating detainees for transfer to Guantanamo detention should that person present a continuing, significant threat to the security of the United States".
"The United States coordinated with the government of the Kingdom of Saudi Arabia to ensure the transfer took place in accordance with established standards for security and humane treatment", Higgins said.
Darbi's transfer was part of a deal reached four years ago, when he pleaded guilty to charges of conspiring with fellow al-Qaida operatives to blow up ships in the Strait of Hormuz.
Saudi state security says al-Darbi arrived just before midnight on Wednesday and that his relatives had been notified.
Al-Darbi issued a statement to The New York Times through his volunteer lawyer, Ramzi Kassem, condemning the practice of sending prisoners to Guantanamo Bay without a trial.
President George W. Bush opened Guantanamo after the September 11, 2001, terrorist attacks to hold and interrogate suspected enemy combatants.
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However, if Iran refuses to allow inspections of sites identified by the stolen archive, it risks an inspection crisis. Trump has frequently voiced his opposition to the "insane" deal, which he has described as the "worst ever".
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In contrast, Trump pledged during his campaign to repopulate the prison, saying he wanted to "to load it up with some bad dudes".
That executive order also rescinded one by former President Barack Obama to close the military prison.
In that order Trump directed Defense Secretary Jim Mattis to make a policy recommendation by April 30 on the transfer of new prisoners to Guantanamo.
The last time a prisoner was transferred from Guantanamo was January 19, 2017, the final full day of the Obama administration.
Trump also asked the Pentagon to re-examine the United States military's detention policy. His family had been informed of his return and arrangements were being made for him to meet them, the spokesman said, confirming that Darbi would now join a "rehabilitation programme".
Mattis on Monday said the US-backed Syrian Democratic Forces, who have been fighting IS, had more than 400 prisoners. Although there was an effort to send those fighters back to their home countries, that was not always easy, he noted. "So this is not simple".
Gen. Mark Martins, the chief prosecutor for the war crimes proceedings at Guantanamo, said in a February Defense Department memo that al Darbi provided "invaluable assistance" to the U.S.