Liberals have been wanting to get their hands on Donald Trump’s tax returns for years. Now, with Democrats holding a House majority with subpoena power, they have a real possibility of getting them.

But they have to be careful about how they go about it.

House Speaker Nancy Pelosi told reporters this month that she’s aware of the “impatience” on the matter but wants to do it right. “It’s not a question of just sending a letter. You have to do it in a very careful way,” she said, according to NPR.

Democrats are looking into an obscure 1924 law that would allow them to request Trump’s returns from the Treasury Department. Republicans and the White House are preparing for a fight, and even Democrats appear split on how aggressively to proceed.

There are plenty of reasons for Congress to want to take a look at a president’s or candidate’s tax returns: The documents can help lawmakers to identify potential conflicts of interest, suggest ways to reform current tax law, and conduct oversight of the IRS, which is supposed to audit the president’s and vice president’s taxes. And in Trump’s case, the argument for reviewing his tax returns is even clearer. He has refused to separate himself from his vast business empire, and questions about whether he is profiting from the presidency have dogged him his entire tenure in the White House.

“The really clear argument is in favor of simply requiring [releasing tax returns] of everyone,” Joe Thorndike, a tax historian and director of the Tax History Project, told me. “The issue is clearly bigger than Donald Trump, although he is the current problem.”

How Democrats could get Trump’s tax returns, explained

Democrats are looking to invoke Section 6103 of the Internal Revenue Code, a statute dating back to 1924. It authorizes the Ways and Means Committee to get the tax return information (personal or business) of any taxpayer — including the president — from the Treasury Department.

Essentially, that means Ways and Means Committee Chair Richard Neal (D-MA) would request Trump’s returns from Treasury Secretary Steve Mnuchin, and Mnuchin would, theoretically, have to comply. If he doesn’t, a court battle would likely ensue. The committee then could vote to have some or all of the tax returns released to the rest of the House, so all members would have access to it — increasing the odds they would get out to the public. There’s a debate as to whether that could then be made public; I’ll get to that later.

University of Virginia law professor and former Joint Committee on Taxation chief of staff George Yin laid out how the process would work in testimony earlier this month. He explained that the authority of Congress to request tax return information was added in 1924 as a co-equal branch of government, and before, only the president had such authority to request and disclose tax returns. Per his testimony:

Section 6103(f) does not place any conditions on the exercise of the authority to obtain tax return information by the Ways and Means Committee. Moreover, it provides no basis for the Treasury Secretary to refuse a request. I believe both features were intentional. Since the president at the time had unconditional access to tax returns, Congress wanted to give its committees the same right.

In 1976, Congress made changes to the law in a couple of key ways relevant to today. First, they eliminated language allowing the committee to submit only “relevant or useful” information to the House. But Yin says the committee still needs a reason to send information to the entire House. Second, they eliminated the ability of the president and any congressional committees not related to tax to disclose tax return information to the public. But tax committees still have that authority, meaning Ways and Means, the Joint Committee on Taxation, and the Senate Finance Committee.

Basically, a handful of committees can still lawfully request someone’s tax returns and at the very least send them to the rest of the House or Senate, assuming they have a legitimate purpose for doing so.

But this might not be that big of a hurdle. “Evidence that Trump has abused our tax laws is plentiful,” Rep. Bill Pascrell (D-NJ), who has been making the case for pursuing Trump’s tax returns under Section 6103 essentially since Trump was inaugurated, said in an emailed statement to Vox. He cited a New York Times investigation into Trump and his family’s tax practices that suggested the family for years engaged in a number of schemes to avoid taxes, and leaked pages from Trump’s 1995 and 2005 tax returns; the 1995 ones show a nearly $1 billion loss.

“Americans have a right to know if their president has paid his taxes, if he has followed the law, and if he is free from financial conflicts of interest,” Pascrell continued. “The law is clear. Under 6103, the Ways and Means Committee chairman is entitled to request Trump’s tax returns — and the Treasury secretary is obligated to deliver them. That’s all there is to it.”

Even if they have a plan, it won’t be easy

Neal is proceeding prudently in an effort to be on as solid a footing as possible if and when he asks for Trump’s returns. Dan Rubin, a spokesperson for Neal, told Politico at the start of the year that he wants to “lay out a case about why presidents should be disclosing their tax returns before he formally forces him to do it.”

But whenever they go for it, the White House promises to be ready. Politico’s Nancy Cook reported that the Treasury Department is “readying plans to drag the expected Democratic request for Trump’s past tax filings … into a legal quagmire of arcane legal arguments.” In other words, Mnuchin probably isn’t just going to happily hand over Trump’s taxes. A Treasury Department spokesperson did not return a request for comment on their plans.

In parallel, Republicans are also coming to Trump’s defense, trying to paint Democrats’ efforts as ones of extreme partisanship and arguing that seeking Trump’s tax returns is a breach of privacy. They previewed their arguments at a Ways and Means Committee hearing on tax law and legislation related to presidential tax returns at the start of the month.

“Every single American has a right to privacy and personal information contained in their tax return,” Rep. Mike Kelly (R-PA) argued in the hearing. He warned that releasing Trump’s returns would open a “Pandora’s box” for Congress to go after virtually anyone’s returns.

Steve Rosenthal, a senior fellow at the Tax Policy Center who testified at the hearing, said the slippery slope arguments Republicans employed are absurd. “This is so different. [Trump] oversees the entire executive branch. In my view, the whole request by the Ways and Means Committee ought to pursue their legislative oversight responsibility, part of the checks and balances of the Constitution,” he said.

There’s a debate over whether making Trump’s tax returns public is legal

Richard Nixon was the first president to normalize releasing his tax returns, when questions about his tax practices came to light as part of a lawsuit (completely unrelated to the Watergate break-in). He released his tax returns in December 1973 in an effort to quell suspicions, but that’s not what happened: The Joint Committee on Taxation found he owed about $475,000 to the government.

After Nixon resigned, presidents since started releasing their tax information as a matter of tradition. Trump, however, hasn’t released any — and he doesn’t have any plans to.

But even if Democrats get Trump’s tax returns, it’s legally questionable if they can make the information public.

Ken Kies, the managing director of the Federal Policy Group whom Republicans called to testify in the Ways and Means Committee hearing, testified that it would be a felony for a member of Congress or staff to publicly disclose tax returns, punishable for up to five years in prison. Others, however, disagreed.

Yin told me he believes that Kies is incorrect in his reading and that Trump’s returns or information from them, if they get from the committee to the House, could also be made public. “The act of submitting to the House creates the possibility of public disclosure, and, in fact, that was what Congress intended when it drafted this entire provision,” he said.

Rosenthal concurred, and pointed to a bipartisan Senate Finance Committee report from 2015 that concluded making taxpayer information available to the Senate and the public as part of an investigation into whether the IRS targeted certain political groups “is clearly permissible under section 6103.”

Republicans argue that they’re afraid that committee Democrats will leak Trump’s tax information once they get it. But it’s not clear how much water that argument holds.

“Republicans are trying to feel their way forward on how they can raise objections,” Rosenthal said.

Democrats are building their case

Democrats also appear to be trying to build a case for why they are pursuing Trump’s tax returns so they have a better shot if it does end up in court — a probable outcome. They are on firmer ground pursuing Trump’s tax returns out of their legislative and oversight duties and not because of a partisan fishing expedition.

John Kovensky at Talking Points Memo recently delved into the matter:

The key test that Democrats would face in any future court battle comes down to whether they have established that Congress has a legitimate purpose in requesting the returns. Asking for them just to release them immediately, or out of spite or a desire to humiliate, could serve as a reason for a judge to strike down the request.

A couple of court cases serve as precedent in the matter. One is Kilbourn v. Thompson, an 1880 Supreme Court case dealing with whether Congress could compel testimony after the House issued a subpoena related to a bankruptcy. The court essentially ruled that the nature of the dispute was between private parties and wasn’t within Congress’s legislative or oversight scope. Another is McGrain v. Daugherty, a 1927 case related to the Teapot Dome Scandal, a bribery scandal in the federal government. In that case, the party subpoenaed refused to comply with a Senate investigation, and the court held that Congress could compel testimony because in that case it was under its oversight purview.

“My reading is that as long as the inquiry fit within one or both of those two responsibilities [oversight and lawmaking], that should be a legitimate purpose, at least based on this case law,” Yin said.

Democrats appear to be aware of what’s at stake.

“I think the idea here is to avoid the emotion of the moment and make sure that the product stands up under critical analysis,” Neal told CNN in January. “And it will.”

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