For nearly seven decades, federal tax law has been clear: Houses of worship are entitled to tax-exempt status, but they’re not allowed to intervene in partisan political campaigns. As The New York Times reported, under Donald Trump, the IRS has unilaterally decided to interpret federal tax law in a new and unique way.

The I.R.S. said on Monday that churches and other houses of worship can endorse political candidates to their congregations, carving out an exemption in a decades-old ban on political activity by tax-exempt nonprofits. The agency made that statement in a court filing intended to settle a lawsuit filed by two Texas churches and an association of Christian broadcasters.

Under the Internal Revenue Service’s new approach, all nonprofit 501(c)3 organizations will continue to enjoy tax-exempt status, but houses of worship will enjoy a new benefit that the agency won’t apply to secular organizations: Churches, temples, synagogues and mosques will be free to endorse candidates, but other nonprofit groups will not.

If you’re thinking this incongruity seems like the sort of thing that will end up in court, you’re not alone.

Longtime readers are probably familiar with the broader fight, but it’s been a while since we went over the basics, so let’s recap and review why this is likely to be a problem.

Before the IRS’s court filing, tax-exempt religious ministries were, of course, free to speak out on moral and spiritual issues of the day and even get involved in ballot referenda related to various policies, but churches and other houses of worship couldn’t intervene directly in political campaigns, taking steps to help (or hurt) candidates or political parties.

The law governing this area was created in 1954, thanks to the efforts of then-Sen. Lyndon Johnson, and for quite a while, it wasn’t especially controversial.

But as the religious right became a more prominent fixture in Republican politics, the Johnson Amendment became problematic. Efforts to create a political machine involving pastors and congregations were stunted by the law — because if a religious leader can’t tell his or her congregation who to vote for without risking the ministry’s tax-exempt status, the movement’s potency had some limits.

And so the religious right decided the Johnson Amendment had to go. In his first term, Trump used to boast that he’d successfully eliminated the Johnson Amendment, although he was either lying or was confused (or perhaps he was confused about the thing he was lying about).

The case for changing the law has long been based on an argument that might seem vaguely compelling at first blush: Those who lead houses of worship should be able to say whatever they wish to their congregants, and it’s not the government’s job to intervene. The First Amendment’s free speech protections, the argument goes, should be applied to ministers in the pulpit.

What’s wrong with that argument? Quite a bit, actually.

When it comes to electioneering and tax law, houses of worship have effectively made a deal with the government: Religious leaders enjoy the benefits of a tax exemption, and in exchange, their ministry will be nonpartisan. Republicans in recent years have said they want to scrap the deal: Churches should get the benefit of a tax exemption from the government, without any of the trade-offs.

As for the First Amendment, note that tax exempt entities, including churches, have long had the option to get involved in partisan politics, endorse candidates and intervene in campaigns to their hearts’ content — but they weren’t supposed to do this while keeping their tax exemption.

As for why the IRS’s new approach matters, there’s potential for dramatic consequences if houses of worship become tools of political campaigns. Imagine the campaign finance mess that would exist if parties, candidates and political action committees could funnel donations through tax exempt churches, free of oversight, all while benefiting from explicit endorsements.

For that matter, imagine if a foreign government, eager to secretly help put a specific candidate in power, decides to funnel money to specific churches, knowing that those ministries would in turn use the resources to support that candidate. The churches would never have to disclose any of this, and the public would be kept in the dark.

The IRS’s new position “fixes” a problem that doesn’t exist. There doesn’t appear to be any great public demand for such a change — most Americans, and even many religious leaders, don’t want churches to endorse candidates — and there’s no reason to create a mess where none currently exists.

And yet, Trump’s IRS is apparently doing it anyway.

This post updates our related earlier coverage.