At the heart of the case is Section 501(c)(4) of the tax code, which mainly addresses social-welfare organizations and advocacy groups. Under IRS rules, a 501(c)(4) organization must be “primarily engaged” in promoting the “common good and general welfare” of society, but not “political campaign” activity.

The problem Freedom Path and other 501(c)(4)s face is simple: They can’t tell what’s legal. The IRS has never defined how much political activity is too much. And even if a group knew the amount of political activity allowed as a percentage of total activities, it still wouldn’t know what qualifies as political. The agency uses an open-ended 11-factor test to determine what counts as “political activity,” without explaining how these factors are weighted or applied.

Judge Cobb ruled that these twin deficiencies “exhibit signs of impermissible vagueness. Taken together, they cross the line into unconstitutionality.” The judge also found a record of “selective enforcement” that “solidifies this vagueness finding,” pointing to the IRS’s targeting of tea-party-aligned 501(c)(4)s during the early 2010s.

While Judge Cobb’s decision dealt a blow to the IRS, it also left the rules in limbo. Because of appropriations riders—provisions attached to spending bills that dictate what an agency can and can’t do with the funds it receives—the IRS can’t conform to the court’s decision by writing a new, constitutional rule on nonprofit political activity.

These riders are a response to the IRS’s tea-party targeting scandal. After the scandal broke, the IRS proposed a new set of rules to clarify what political activities are permissible for 501(c)(4)s, but the proposed rules were overly broad and would have labeled too many activities as political. Congress understandably stopped the IRS from going down that road.

Congress has an important role to play. Lawmakers would be wise to remove the IRS rider from the next spending bill so that the agency can comply with the Freedom Path court ruling and the First Amendment.

Meanwhile, the IRS needs to stop policing speech. As a tax-collection agency, it lacks expertise and has demonstrated incompetence at this function. Myriad federal and state campaign-finance laws already regulate political activity, and separate specialized agencies, including the Federal Election Commission, administer those laws.

The IRS could defer to those laws and agencies in determining what counts as political campaign intervention by nonprofits. While some of those campaign laws are also too vague and broad, they are generally better than the IRS rules. If the agency does this, nonprofits would no longer have to comply with two different standards—one from the IRS and one from the campaign-finance laws.

Congress could consider going even further by eliminating the tax code’s restrictions on political activity by nonprofits, other than perhaps for (c)(3) charities and educational institutions, which uniquely receive a tax subsidy in the form of deductible donations.

Congress thrust the IRS into regulating political speech by distinguishing 501(c) entities such as the American Civil Liberties Union or National Taxpayers Union, which have political-activity limits, from purely political entities such as the Republican National Committee or Biden for President, which operate under Section 527 of the tax code. All of these nonprofits generally pay no taxes unless they engage in profit-making activities. Insofar as they should be regulated for their political activity, that should be the exclusive function of campaign-finance regulators.

The Freedom Path decision presents Congress with an opportunity to stop the IRS from using the tax code to police political debate.