MADISON, Wisconsin - A U.S. group representing atheists and agnostics has filed a federal lawsuit arguing that the Internal Revenue Service is violating the Constitution by allowing tax-exempt churches and religious organizations to get involved in political campaigns. The Freedom from Religion Foundation argues that churches and religious organizations have become more involved in political campaigns, "blatantly and deliberately flaunting the electioneering restrictions." The lawsuit, filed in Wisconsin, cites several examples, including full-page ads that ran this fall in The New York Times and other newspapers by the Billy Graham Evangelistic Association that featured a photo of renowned evangelist Billy Graham urging Americans to vote along biblical principles. Graham met in October with Republican presidential challenger Mitt Romney and pledged to do "all I can" to help him. The lawsuit argues that the IRS is not enforcing the federal tax code, which prohibits tax-exempt religious organizations from electioneering. The suit says not enforcing it is a violation of equal protection rights because the same preferential treatment is not provided to other tax-exempt organizations such as the Freedom from Religion Foundation. The lawsuit asks that the IRS initiate legal action against any churches or religious organizations that are believed to be violating the restrictions.