The Council of State has issued a final and irrevocable decision granting one of eight Turkish servicemen accused by Ankara of participating in the botched coup of 2016 asylum.
According to sources, judges at Greece's highest administrative court upheld the Turkish officer's asylum request in a decision that is expected to influence the course of the other seven servicemen's applications.
Two of the servicemen have already been released from police custody as the maximum period for detaining a suspect has expired, with the other six expected to join them within the next few days.
Greece's Supreme Court has already ruled against their extradition to Turkey.
Wednesday's ruling is expected to put a further strain on already tense relations between Athens and Ankara.