The Fiji Court of Appeal has ruled that the controversial army officer, Lt Col Filipo Tarakinikini, is absent without official leave and has ordered him to return to the country.
The officer is currently working for the United Nations Peacekeeping Department in New York and has refused to return, instead sending a resignation letter last year.
When the military commander, Commodre Frank Bainimarama, refused to accept it, Lt Col Tarakinikini won a High Court ruling upholding the resignation.
He also claimed damages of 250 thousand US dollars from the Fiji military and wanted a court order to stop investigations into his alleged involvement in the May 2000 coup.
But the Court of Appeal has unanimously rejected the High Court decision and ruled that under the Republic of Fiji Military Forces Act, an officer is not free to resign at will.
The appeal court judges also ruled that investigations into Lt Col Tarakinikini can continue.
The officer is reported to be making a fresh attempt to resign direct to Fiji's president who is commander in chief of the military.