Iowa ethics officials sent a letter to the National Organization for Marriage questioning the group about possible violations of campaign finance laws, reports the blog HRC Back Story.

Last week, NOM launched its Reclaim Iowa Project, a multiyear effort to pass a constitutional amendment that would overturn the state supreme court’s unanimous April 2009 decision legalizing same-sex marriage. NOM purchased $86,068 worth of advertisements in support of Stephen Burgmeier (pictured), a Des Moines–area state house candidate who wants to put marriage equality to a public vote.

The letter from the Iowa Ethics and Campaign Disclosure Board to NOM executive director Brian Brown, dated August 27, warns NOM that it will need to register as a political action committee if people make donations of more than $750 for “express advocacy activities.” It also clarifies that NOM will need to disclose its donors, in spite of the organization’s reported promise of anonymity to contributors.

“The independent expenditure process in Iowa is not a vehicle to shield political contributions,” says the letter.

NOM is also being questioned about its activities in Maine, where it provides support to Stand for Marriage Maine, the group that succeeded in placing a referendum on the new marriage equality law on the November ballot.