In a 36-page opinion formally released Thursday, U.S. District Judge Henry H. Kennedy Jr. called Odaini's continued detention "unlawful" and said he'd "emphatically" grant Odaini's petition for a writ of habeas corpus.

The ruling issued secretly last month but published Thursday sets the 26-year-old Odaini up for potential release, though when and where he'll go remains unclear. The ruling also represents the latest defeat for U.S. officials in their efforts to keep Guantanamo detainees behind bars.

"(U.S.) officials kept a young man from Yemen in detention in Cuba from age eighteen to age twenty-six," Kennedy wrote. "They have prevented him from seeing his family and denied him the opportunity to complete his studies and embark on a career."

Pointedly, Kennedy added that "the evidence before the court shows that holding Odaini in custody at such great cost to him has done nothing to make the United States more secure."