The National Organization for Marriage has fought for years to keep its donor list secret, saying doing so would put its contributors at risk for harassment and intimidation.
A lawyer for the organization vowed to appeal the ethic commission's decision in state court, and members of the panel said they expect litigation to continue for at least a year.
Under Maine law, groups must register if they raise or spend more than $5,000 to influence a statewide ballot question.
The National Organization for Marriage gave nearly $2 million to Stand for Marriage Maine for the 2009 referendum, or more than 60 percent of the political action committee's expenditures, ethics investigators said in a report released earlier this month.
Investigators found that the national group "intentionally set up its fundraising strategy to avoid disclosure laws" by not allowing donors to mark that the funds were to be used to defeat same-sex marriage in Maine. Investigators say emails soliciting donations and the group's finances clearly show that more than $5,000 was raised with the purpose of assisting the Maine campaign.
Walt McKee, chairman of the ethics panel, said not fining the group would amount to "accepting a mockery" of Maine's disclosure laws. It's thought to be the largest campaign finance penalty in the state's history.
The organization argues that by not raising money specifically earmarked to influence the Maine gay marriage question, it was explicitly working to stay within the bounds of the state's law. It says that disclosing names will chill future donations.
"We didn't create a scheme, we tried to follow the law," Brian Brown, president of the Washington, D.C.-based organization, told the four-member panel on Wednesday.
Brown, who served as executive director of the National Organization for Marriage in 2009, was one of three members of the committee that led the Stand for Marriage Maine PAC.
Commissioners said his dual role and the fact that the national group controlled a majority of the PAC's funds was problematic for its argument that the funds weren't raised to influence the Maine campaign.
The group says that it's being targeted because of its stance on gay marriage and that groups on the other side of the issue such as the Human Rights Campaign followed the same guidelines.
State investigators said that its examination of the National Organization for Marriage actions was brought by a specific complaint and that the organization could have sought a similar investigation into the Human Rights Campaign.
John Eastman, a National Organization for Marriage lawyer, said that it intends to file a complaint against HRC in addition to filing an appeal.
Fred Karger, who leads the gay-rights group Rights Equal Rights and filed the complaint in 2009, praised the panel's decision and said he's confident that Maine would continue to fight the group in court.
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