Lawyer and opposition Democratic Action Party (DAP) chairman Karpal Singh had allegedly questioned the removal of Mohammad Nizar Jamaluddin as Perak state chief minister by the Sultan of Perak.
Justice Azman Abdullah gave his ruling after finding that Singh had failed to prove reasonable doubt against his case.
Singh, a 73-year-old outspoken, wheelchair-bound politician, was found guilty of insulting the Sultan of Perak in 2009. The court fixed March 7 for sentencing and mitigation.
He was alleged to have said that the removal of Mohammad Nizar as chief minister by the Sultan could be questioned in a court of law.
Malaysia forbids criticism of its revered ethnic-Malay Islamic royals.
Singh plans to appeal against his conviction, which sparked an outcry against the government's use of the decades-old Sedition Act.