The lawsuit was filed in January by the American Civil Liberties Union on behalf of other political parties, a weekly newspaper and a political consultant.
Edmunds agreed with their claim that it's illegal to allow only Michigan's two major political parties to get information on who voted and whether they took a Republican or Democratic ballot.
The dispute over whether to seat Michigan's Democratic delegates at the party's national convention remains unresolved.
Secretary of State Terri Lynn Land, the defendant, was required by the law to give the political parties that voter information within 71 days of the primary. That deadline was Wednesday. But it became moot with the judge's decision.
Michigan Republican Party spokesman Bill Nowling said after the ruling that the party was fine with the outcome.
"From our standpoint, it has never been about who has access to the list, it has been about whether or not Michigan should move its primary up, and we did that," he said.
Michigan's Democratic Party had no immediate comment.
