The court said in its ruling issued Friday that the measure violated the state's constitutional provision against asking voters to cast one vote on two unrelated issues. The court directed Secretary of State John Gale not to certify the measure or place it before voters on Nov. 4 ballot.
The measure would have asked voters to approved the betting on historic horse races as well as how the proceeds should be divided.
Pat Loontjer, executive director of Gambling with the Good Life, filed the lawsuit. The group had previously asked Gale to keep the amendment off the ballot but Gale rejected the request.