By Dan Merica, CNN

Washington (CNN) - When Pastor Jim Garlow took to the pulpit September 28, he was thinking two things.

He first thought that the sermon he was about to give, a sermon in which he was going to endorse a handful of 2012 Republican presidential hopefuls, might earn him a letter from the IRS, possibly even a visit from an agent. By endorsing candidates, Garlow was about to violate the Johnson Amendment, which prohibits tax-exempt churches from engaging in political activity.

But according to Garlow, the senior pastor at Skyline Wesleyan Church in La Mesa, California, the conviction that "our nation, economically and morally, is in such a condition that America as we have known it for its 200-plus years is on the verge of disappearing" was enough of an impetus to break the rules.

Garlow's sermon was part of a wider effort by the Alliance Defense Fund, a legal organization that since 2008 has hosted Pulpit Freedom Sunday, a day when they encourage and promise to protect pastors who willfully violate the Johnson Amendment and endorse from the pulpit.

The movement is growing. While it started with 33 churches in 2008, 539 churches participated in 2011.

"We basically see Pulpit Freedom Sunday as a means of protecting a pastor's right to speak freely from the pulpit without fearing government censorship in any way," said Erik Stanley, ADF's senior legal counsel and organizer of Pulpit Freedom Sunday.

And so far, the effort has received little to no response from the IRS. Though the agency did not respond to CNN's request for specific numbers, according to Stanley, the majority of the messages go unnoticed and only a handful of pastors receive letters.

This trend of non-enforcement has emboldened pastors and the ADF. When Garlow weighed his decision to participate, he said he knew the IRS was not challenging the churches, and that contributed to his willingness to speak.

This current loophole of non-enforcement, said the Rev. Barry Lynn, executive director of Americans United for the Separation of Church and State, means Americans can expect a huge jump in endorsements from the pulpit in the 2012 election.

"When the Alliance Defense Fund says to churches that the IRS aren't investigating them right now, that gives the churches the sense we can get away with anything," said Lynn, who has been director of Americans United for 20 years.

As for the reason for the loophole, it depends on what side you ask. Stanley and the ADF contend that the reason officials aren't investigating is because they don't want to be challenged in court and the IRS may be disorganized.

Lynn and Americans United contend that a simple bureaucratic decision as to what level of IRS official can initiate an investigation led to the current loophole. Lynn said that Obama administration has been unwilling to change the regulation.

"If it becomes a permanent loophole, this would create a giant loophole for friendly pastors to endorse them and take out ads," Lynn said.

According to Naomi Riley, a contributor to Philanthropy Daily, a publication that covers nonprofits like churches, the issue ebbs and flows around elections.

"I think the issue heats up as it gets closer to elections," Riley said. "Each side thinks that when another administration is in power they are looking more in the churches than they should be, but obviously Republicans are more worried about Democrats looking to enforce this rule."

The current vagueness in policy is new; in the past, the IRS has investigated churches that they thought violated the Johnson Amendment.

Four days before the presidential election in 1992, the Landmark Church in Binghamton, New York, ran a full-page ad in USA Today that said, "Christians Beware," and was followed by a list of Clinton's positions on homosexuality, abortion and the distribution of condoms. At the bottom, the church asked for donations to help pay for the ad.

According to Lynn, Americans United filed a complaint, and in 1995 the church lost its tax-exempt status.

Landmark Church Pastor Dan Little took the IRS to court, arguing that the agency was violating the church's First Amendment rights and that the agency was only able to revoke the tax-exempt status of a "religious organization," not an actual church.

Both a federal judge and an appeals court rejected both arguments.

In Lynn's opinion, this ruling is evidence that if the IRS enforced the Johnson Amendment, it would be able to revoke church's tax-exempt status.

Jeffrey Toobin, CNN's senior legal analyst, is not so sure that there would be a similar result if the IRS initiated another case.

"The court is much more hostile to anything that could be interpreted as a restriction on speech and the political realm," Toobin said. "Even if it is the withholding of a subsidy, the Supreme Court is much more favorably inclined towards religious groups than it has been in the recent past."

But Toobin acknowledged that without IRS enforcement action, there is no "live controversy" to rule on. Though the numbers taking part in Pulpit Freedom Sunday may continue to grow, unless the IRS goes after a church, none of the churches will have legal standing to bring a lawsuit.

"These are values in conflict," Toobin said. "The constitution mandates a degree of separation from church and state. But it also mandates freedom of speech, and this is an example of how society, in the courts, has to sort out apparent conflicts between those ideas."

According to Wayne B. Giampietro, the general counsel of the First Amendment Lawyers Association, there is a fine line between a preacher talking as an individual and a preacher speaking for the church.

"It is one thing for a preacher to be talking just as an individual," Giampietro said. "He has an absolute right to endorse anyone they want, but once they start saying this comes from the church, that is when you run into problems."

This issue arose at last month's Values Voter Summit. Americans United sent a letter to the IRS after Pastor Robert Jeffress, the same pastor in the news recently for calling Mormonism "a cult," endorsed Texas Gov. Rick Perry in his speech and posted that speech on his church's website. Americans United contended that when Jeffress posted the video to the website, it amounted to an endorsement from the church, not just the pastor.

Giampietro said he can't predict how the court would go, but he said the IRS has a right to withhold tax exemption from any group, and because there is no right to tax exemption, taking a church's tax exemption away is not violating their First Amendment rights.

Back in La Mesa, Pastor Garlow said he plans to participate in Pulpit Freedom Sunday next year.

According to Stanley at the Alliance Defense Fund, he will be far from alone. Because of the popularity of the event, organizers are now making it a weekend-long protest so that churches can participate on Saturday and Sunday. Stanley said he expects the number of participating churches to go up again.

Garlow's sermon was not specific. "I didn't endorse a singular candidate. I said here are the ones that violate scripture and here are the ones who are in the scope of scripture."

After the sermon was over, Garlow said people cheered and asked him why he didn't speak out like this more often. The members of his congregation "were enormously hungry for me to speak out on these issues," Garlow said.

But even though the issues Garlow spoke about - gay marriage and abortion - were important to him, he said Pulpit Freedom Sunday represents larger feelings in America.

"The bigger picture in all of this is there is a groundswell that is taking place," Garlow said. "... Pastors and people of faith are saying that is it, that is enough, we must speak out."