Members of the commission on Monday decided unanimously that Navalny, a lawyer turned anti-corruption campaigner, isn't eligible to run in the election because of a controversial conviction in a fraud case.
Navalny submitted his official nomination for the vote on Sunday as hundreds of his supporters attended a campaign event in Moscow and endorsed his candidacy. He could have run in the election if the conviction, which he insists is politically-motivated, was canceled or if he could receive a special dispensation.
He was viewed as a main challenger to President Vladimir Putin in his bid for reelection. Putin is planning to run as independent, hoping for support from more than one political party.
Navalny, who has led a far-reaching campaign against corruption in the government, said in a message after the election regulator issued its ruling that he would boycott the vote.
“The procedure that we're invited to take part [in] is not an election ... Only Putin and the candidates he has hand-picked are taking part in it,” he said, adding, “Going to the polls right now is to vote for lies and corruption.”
Navalny also said that the decision to bar him from the election was "not against me, but against 16,000 people who have nominated me, against 200,000 volunteers who have been canvassing for me.”
Election authorities said the criminal conviction against Navalny effectively made it impossible for him to compete in the election.
Ella Pamfilova, who serves as the Central Election Commission chief, had told Navalny before the Monday announcement that the electoral body was maybe interested in putting the opposition figure on the ballot, but the conviction did not allow it.