The High Court has ruled that Mark Serwotka is the official General Secretary of the Public and Commercial Services Union.
The court ruled that the outgoing General Secretary, Barry Reamsbottom, had no legal right to remain in office after his five-year term ended on 31 May 2002.
Reamsbottom had declared Serwotka's victory void at a National Executive committee, claiming the election was unlawful.
However Serwotka, PCS General secretary, said he was pleased that the court accepted his victory as valid: "I was elected General Secretary on a programme of defending PCS members' jobs, re-establishing national civil service pay and conditions and opposing privatisation.
"PCS will now continue working for high quality public services and improving the service that the union provides to members and representatives at the workplace," he said.