A five-judge bench in a unanimous decision ruled that the President's term was limited to five years by the 19th amendment to the constitution that he himself initiated after winning the 2015 elections.
The bench headed by Chief Justice Priyasath Dep told Sirisena that he had only five years in office as a result of the 19th amendment although he was elected initially for a six year term, the local media reported.
However, the 19th amendment clearly spelt out that Sirisena was entitled to a five year term after voluntarily trimming the tenure by one year.
The move has also put Sirisena on a collision course with his senior coalition partner. It could also backfire on Sirisena's campaign for the February local council elections.
The United National Party-led government of Prime Minister Ranil Wickremesinghe was banking on a presidential poll by January 2020, six months ahead of the next general election.
Sirisena has previously said he was going to be the last executive president of the country because he was going to abolish that office and turn the country into a full parliamentary democracy.
There is known to be growing tension between the President and the Prime Minister after Sirisena recently declared that he believed that the United National Party (UNP)-led government was probably more corrupt than the Mahinda Rajapaksa regime they had toppled together. (ANI)