Some 1,400 pastors plan to break the law this weekend by endorsing political candidates in what's being called Pulpit Freedom Sunday.
Organizations like the Alliance Defending Freedom first launched the event in 2008.
The move is a direct challenge to Internal Revenue Service rules prohibiting churches from participating in partisan campaigning for or against political candidates.
The regulation was implemented in 1954. In 2009, a U.S. District Court ruled the IRS no longer had appropriate staff to investigate churches, following a reorganization that changed the agency's authority.
The ADF, however, said it still takes the IRS restriction seriously.
Jim Garlow, pastor of Skyline Wesleyan Church in California, said the prohibition has caused religious leaders to shy away from speaking about what they see as theological truth, such as the belief that homosexuality is biblically unacceptable.
"Every pastor and every church has the right to decide what their pastor preaches from the pulpit and to not have that dictated to them by the IRS," the ADF attorney Erik Stanley said.