COLOMBO: Sri Lanka's Supreme Court on Thursday ruled that the dissolution of Parliament by Maithripala Sirisena was "unconstitutional", in a major setback to the president whose controversial decisions have plunged the island nation into a constitutional crisis.A seven-member apex court bench said that the president cannot dissolve Parliament till Parliament completes a 4 1/2 year term, the Colombo Gazette reported.Sri Lanka is going through a major political crisis since October 26 when President Sirisena, in a controversial move, sacked Prime Minister Ranil Wickremesinghe and installed former strongman Mahinda Rajapaksa in his place.He also dissolved Parliament and called for a snap election on January 5.Sirisena sacked the 225-member Parliament when it appeared that Rajapaksa would not be able to muster the support of 113 MPs. Wickremesinghe on the other hand commands a majority. As many as 13 petitions were filed against Sirisena's November 9 order sacking the Parliament, almost 20 months before its term was to end.The Supreme Court on November 13 had issued an interim order ruling Sirisena's gazette notification as temporarily illegal and halted the preparations for snap polls.