The Economic Community of West African States Court of Justice found the authorities on the Atlantic Ocean island nation carried out Saab’s arrest before a so-called Red Notice had been issued by Interpol.

“We found his arrest by the criminal police of Cape Verde was arbitrary and subsequent detention throughout the period until today was illegal,” Justice Edward Amoako Asante said Monday at the Abuja-based tribunal. “Cape Verde should immediately release the applicant from their custody and immediately stop all processes to extradite him.”

The ruling may complicate efforts by Washington to crack down on officials accused of corruption in Venezuela. U.S. officials believe Saab holds numerous secrets on how Maduro and his inner circle allegedly looted hundreds of millions of dollars from state coffers.

Saab, 49, has been indicted by a U.S. federal court in Florida on federal money-laundering charges related to bribing Venezuelan officials. He has denied the charges through his lawyers.