The Court of Appeal has ruled in favour of the Professional Firefighters Union, saying it has the right to strike.
Earlier this year, the Employment Court told the union it could not take industrial action, following a breakdown in negotiations with the Fire Service Commission.
Talks had been under way since December last year.
In June this year, the commission asked the union to stop industrial action planned for July.
The matter went to the Employment Court, which said the union should not have given notice of a strike before mediation took place.
The Court of Appeal has now found that the Employment Court did not have the power to order union members to stop a strike.
The union is seeking a pay rise of 8.9%. It has been offered 2.5% by the Fire Service Commission, which says the amount being asked for is unaffordable.