About 1,400 pastors will do something on Sunday that most Americans probably don’t know is against the law: They will tell their congregations just what they think of Democratic President Barack Obama and Republican challenger Mitt Romney.

As part of “Pulpit Free Sunday” on Oct. 7, religious leaders from across the nation will endorse political candidates in defiance of Internal Revenue Service regulations on tax-exempt organizations, such as churches. As a result of a 1954 law known as the Johnson Amendment, churches accorded tax-exempt status by the federal government are prohibited from participating in partisan campaigning for or against political candidates.

The IRS ran into problems enforcing the rule in 2009, after the U.S. District Court in Minnesota ruled that the IRS no longer had the staff to investigate places of worship that may be in violation of the rule. New procedures for conducting church audits have been pending since then.

The Alliance Defending Freedom, formerly known as the Alliance Defense Fund, began organizing its “Pulpit Free Sunday” in 2008 in response to the IRS regulation. The ADF is a Christian legal ministry that specializes in taking cases where they believe “religious liberty” is at stake, most notably in defense of businesses or organizations that discriminate against gays and lesbians.

The goal of Sunday’s event, according to ADF senior legal counsel Eric Stanley, is to force the IRS to come down on participating churches so the group -- which includes 2,200 attorneys -- can take on the constitutionality of the Johnson Amendment.

"The IRS has the ability and authority to regulate their sermons. We are giving them the opportunity to do that and if they challenge that, we will challenge that in court,” Stanley told CNN. “It is all about creating a test case to find the Johnson amendment as unconstitutional.”

CNN reports ADF, which some critics have accused of being a Republican front group, was unable to put them in touch with a church that plans to endorse President Barack Obama this Sunday.