The National Organization for Marriage’s lawsuit against the IRS may be the case that finally breaks the IRS’s “omerta” code.

In the spring of 2012, NOM’s private tax-return data turned up splashed on the Web site of its chief political opponent, the Human Rights Campaign. The leak plainly came from the IRS, because the tax return published on the site was stamped with special codes the IRS uses on electronically filed returns.

The leaked, confidential information included a list of NOM donors. Making their names virtually invited harassment of these people.

Incidentally, the chairman of the Human Rights Campaign, Joe Solomonese, happened to be a co-chair of President Obama’s re-election campaign.

Leaking private tax records is a felony, punishable by up to five years in prison. But the IRS has stonewalled NOM’s efforts to find out what happened, even going so far as to insist it legally can’t even say it’s investigating. The supposed reason? Because laws that prevent the disclosure of return information, it claims, also protect anyone who’d be the target of an investigation into breaking those laws, and even the mere fact that the IRS is investigating.

The misuse of the IRS for political purposes by the government in power is a grave threat to our freedom, and democracy itself. Yet this case is far from unique.

We now know senior IRS officials delayed tax-exempt status for dozens of Tea Party groups until after the 2012 election. Dr. Ben Carson says he was audited for the first time just after he criticized President Obama to his face at the National Prayer Breakfast. And Mitt Romney superdonor Frank VanderSloot said he was audited three times last year, after being publicly named as one of eight “shady” donors to Romney by the Obama campaign.

Yet the IRS has consistently refused to open up about these outrages. IRS Director of Exempt Organizations Lois Lerner “took the Fifth” when questioned about her involvement by the House Government Oversight and Reform Committee in May, and later retired.

The NOM lawsuit may be able to break this stonewall. NOM wants a jury trial for financial damages. The chairman of its board, John Eastman, says this is the most promising legal means for NOM to uncover who committed this crime and demand he or she be prosecuted.

When NOM first complained about the illegal release of its tax returns, the IRS gave NOM an investigation number and interviewed NOM employees. When reporters for the news organization ProPublica inquired, they were told that the Treasury General Inspector for Tax Administration had “found these instances to be inadvertent and unintentional disclosures by the employees involved.”

Since then, NOM has repeatedly filed Freedom of Information Act requests to learn the results of the investigation. But the IRS has taken the absurd position that the victim of the crime isn’t entitled to know even whether the investigation has been concluded. The IRS rejected NOM’s last appeal on June 25, insisting it “can neither admit nor deny the existence of any records responsive to your request. . . Information concerning potential non-tax Title 26 violations . . . constitutes the return information of the person(s) being investigated.”

NOM doesn’t know who committed this crime. But it has discovered that some IRS officials who’d have access to the returns — like a senior manager for tax-exempt organizations — were photographed at an HRC Christmas party just a few months before the returns showed up on HRC’s Web site.

Rep. Dave Camp (R-Mich.) head of the House Ways and Means Committee has been quietly conducting an investigation of the illegal disclosure of NOM’s private donor information, with a final report due early next year. And Rep. Darrell Issa (R-Calif.) just announced the House Government Oversight Committee will investigate as well.

But there’s no guarantee either probe will get to the bottom of the affair, and NOM — and the American people — deserve answers.

“The fact the IRS is stonewalling so hard suggest the wrongdoing goes high up,” says Eastman. “All we want to know is who committed this crime and see justice done for all federal taxpayers. For the IRS to use disclosure to shield people it wants to shield, instead of protecting taxpayers, is an outrageous and unbelievably dangerous thing; the government can use the IRS to punish any speech it doesn’t like.”

Some things go deeper than right or left; the use of the IRS to punish political enemies ought to be one of them

Maggie Gallagher, who founded NOM, is a fellow at American Principles Project.