Internal Revenue Service Commissioner John Koskinen (Jacquelyn Martin/Associated Press)

Miriam Galston is a law professor at George Washington University.

As the 2016 presidential and congressional races heat up, many people increasingly worry about the large amounts of “dark money” from undisclosed sources being used to finance election campaigns. A recent ill-conceived statement by Internal Revenue Service Commissioner John Koskinen could make this crisis even worse. A key class of tax-exempt groups, he said, could spend up to 49 percent of their revenue on politics without losing their tax-favored status. Koskinen even suggested that this position corresponds to the intent of Congress.

Nothing could be further from the truth. The commissioner’s statement was inconsistent with the legislation under which the IRS operates, contravenes a long line of judicial opinions and is bad public policy. Here’s why:

Section 501(c)(4) groups have become the vehicle of choice for those who want to raise and spend money on political campaigns without disclosing the source of those funds. The groups derive their name from the section of the Internal Revenue Code describing “social welfare organizations” that qualify for exemption from taxes on their net income. To fulfill a social welfare mission, according to IRS regulations, the groups must be “engaged in promoting in some way the common good and general welfare of the people of the community.” Although the terms are vague, case law and IRS rulings have established that “social welfare” does not include commercial activity and other kinds of private benefit. Nor, according to the IRS, does political campaign activity — itself a private benefit — fall within the definition of social welfare.

How, then, can so many 501(c)(4) groups pour millions of dollars into campaigns and still maintain their tax-exempt status? The answer allegedly lies in the language of an IRS regulation stating that social welfare groups must be “primarily engaged” in promoting the common good and civic betterment. Some politically active groups claim that “primarily” means “more than half” and that their 501(c)(4) exemption remains valid if they limit what they spend on electioneering to 49 percent of their total expenditures.

What supports this interpretation? The statute that authorizes the tax exemption states that 501(c)(4) groups must be “operated exclusively for the promotion of social welfare.” IRS regulations converted “exclusively” into “primarily.” This shift may have been reasonable to avoid a strictly literal interpretation of “exclusively,” since zero tolerance could cause some 501(c)(4) organizations to lose their exemption because of an honest misunderstanding over which activities would be considered political. But it is not reasonable to stretch “primarily” to mean merely 51 percent.

Why not? For decades, the IRS has denied 501(c)(4) status to groups engaged in significant amounts of commercial or other activities that benefit private parties more than incidentally. In the ensuing court cases, the government’s own litigating position consistently has been that any private benefit derived from a 501(c)(4) group’s activities “cannot be substantial.” Five appellate federal courts and numerous lower courts have agreed, holding that a single substantial non-social-welfare purpose will prevent a group from maintaining its 501(c)(4) status. In the words of one court, a group’s activities may be “totally commendable,” but this alone does not justify social welfare status. Per the IRS’s own regulations, political activity is not social welfare.

Thus, there is no statutory, regulatory or judicial authority supporting Koskinen’s 49 percent-51 percent interpretation.

As a policy matter, the “insubstantial” interpretation makes sense as well: Congress sought to give favorable tax treatment to organizations engaged exclusively in social welfare — by which it meant a public purpose, not a partisan one. Congress also created a different tax-favored vehicle for what it labeled “political organizations,” but these organizations are subject to disclosure requirements. That is why dark-money groups want to use Section 501(c)(4) rather than get an exemption as political organizations. The IRS should be enforcing — not subverting — congressional intent.

The 49 percent-51 percent advocates also want the test to measure only expenditures, not time spent, volunteer efforts or even the importance of campaigning to the group’s mission. For them, a group could form for the purpose of being a dark-money vehicle but still be a 501(c)(4) organization if political expenditures were kept to 49 percent of total spending. This interpretation perverts Congress’s intent to favor groups with a social welfare mission, not a private purpose.

This dispute is not about stifling free speech. The Supreme Court has stated emphatically that tax exemptions are a subsidy and that there is no constitutional right to tax-subsidized speech. This principle has been endorsed by liberal and conservative justices. Its soundness has been amply demonstrated in recent years as groups have abused their 501(c)(4) status to raise extraordinary amounts of money from secret donors for political campaigns.

Against this backdrop, it is difficult to explain the commissioner’s stance. Koskinen should admit that his statement was in error and withdraw it before it sows even more confusion.