PORTLAND — A state law that sets detailed reporting requirements for political action committees is unconstitutional when applied to referendum campaigns, a federal judge ruled Friday.

U.S. District Judge D. Brock Hornby said the PAC registration requirements are too broad for noncandidate ballot measures and violate First Amendment guarantees of free speech.

According to Maine’s election statute, anyone who spends more than $50 on a ballot issue becomes a PAC and must register with the state, disclosing personal bank accounts, assets and the names of contributors to their cause.

“I think that the judge properly interpreted the protections of free speech under the First Amendment and properly found that the Maine statute was way over broad,” said John McArdle, a lawyer for plaintiff Paul Volle. “What can you do for $51? Put a sign up on your lawn or have coffee to discuss an issue?”

Volle of the Christian Coalition of Maine took the issue to court because he wanted to solicit contributions to campaign in support of the abortion procedure ban on the Nov. 2 ballot. But Volle contended the PAC requirements were too burdensome, and supporters shied away because they didn’t want their names or contributions to be divulged, as required by state law.

“What the court had trouble with is the scope and broadness of the statute,” said Assistant Attorney General William Stokes. “The court said the extent of the information that the state is requiring them to disclose is too broad.”

Stokes said Hornby’s ruling was not a total defeat for the state.

“The statute has been invalidated at least in part, but the constitutional principle that we can require some filing is upheld, and now it’s just a question of fine-tuning the statute.”

At a hearing last week, Volle said that if the judge sided with him, he would begin asking for contributions in support of the referendum to ban certain late-term abortions and a referendum against a proposed gay rights law in Falmouth.

For now, Volle and others have a “free pass” to campaign in support of referendum issues, Stokes said.

Both Stokes and Hornby said it will be up to the Legislature to define in the future the requirements of a political action committee.

“If Maine wishes to preserve some limited regulatory oversight for ballot measure advocacy fund raising and spending, as I have suggested it can under current Supreme Court precedents, then there are legislative decisions to be made that involve the definition of a political action committee, what information is to be reported and when,” Hornby wrote in his ruling.