PORTLAND -- A federal judge will rule Wednesday on whether the state may require two national organizations that are working to repeal Maine's gay-marriage law to disclose their contributors.

The National Organization for Marriage and American Principles in Action have challenged the state campaign finance laws that apply to ballot question committees, arguing that requiring them to disclose their contributors violates the free speech protections in the First Amendment to the Constitution.

"The requirements here ... are sufficient to chill parties from supporting the plaintiff and others," the lawyer for the national groups, Josiah Neeley, told Justice D. Brock Hornby during Monday's hearing in U.S. District Court.

The organizations are asking Hornby to block Maine's Commission on Governmental Ethics and Election Practices from enforcing the disclosure law and following through with an investigation.

The National Organization for Marriage has given $1.6 million to the political action committee Stand for Marriage Maine, which is leading the fight to overturn the same-sex marriage law passed in May.

American Principles in Action has produced two video spots in favor of the repeal and is seeking money to air them as commercials in Maine.

The ethics commission voted 3-2 on Oct. 1 to investigate whether the National Organization for Marriage was subject to ballot question committee reporting requirements, and whether it violated those requirements. Violations can lead to fines, and, in the most extreme cases, a small amount of jail time.

Assistant Attorney General Phyllis Gardiner represented the commission before Hornby on Monday.

"The compelling interest for the public is to know who's spending money to influence their vote," she said afterward, noting that voters may want to know whether they are being lobbied by people from within or outside Maine.

She said the law doesn't restrict how much money groups raise or spend.

Gardiner said the lawsuit is the first challenge of the state's requirement for ballot question committees to register and report contributions.

The state law requires anyone raising or spending more than $5,000 on a ballot question in Maine to disclose anyone who contributed more than $100 for that purpose.

Neeley said the National Organization for Marriage raises money across the country to oppose efforts to legalize gay marriage. It can be hard, if not impossible, he said, to determine whether a given contribution was made to influence the Maine initiative.

The group noted several e-mail solicitations it sent out, mentioning Maine along with other states.

Neeley said after the hearing that there are important reasons not to require disclosure.

"There's a long tradition in this country relating to anonymous speech," he said. Particularly in the Internet age, a donor to a political cause could be subject to harassment or invasion of privacy, and that could affect people on either end of the political spectrum, he said.

Gardiner said the requirements don't appear to have had a chilling effect. She said the National Organization for Marriage has contributed $1.1 million to the effort to repeal the law since Oct. 1. Stand for Marriage Maine said in its campaign reports that it received contributions of $10,000 to $500,000 on 11 separate dates.

Gardiner told Hornby that deciding whether a contribution was intended to influence Maine's ballot question could be based on the solicitation that prompted the donation.

The ethics commission will not meet again until Nov. 19, and the results of its inquiry won't be determined until well after Question 1 is decided.

If the judge does not grant the temporary restraining order, the issue of whether the national groups must comply with the law will be decided by the commission and, in time, by the federal lawsuit.

If Hornby does grant the restraining order, the national groups will be able to raise and spend in the week before the campaign without having to fear violating the state's reporting requirements.