The White House just rejected a subpoena House Democrats had issued for President Donald Trump’s tax returns — continuing a weeks-long legal battle between the administration and Congress.

In April, House Democrats asked the IRS to hand over Trump’s returns. After missing two deadlines, Treasury Secretary Steven Mnuchin officially denied Democrats’ request, prompting House Ways and Means Committee Chair Richard Neal (D-MA) to subpoena them. The administration rejected that subpoena on Friday, citing the same reasoning he used when originally refusing the request.

“I am informing you now that the Department may not lawfully fulfill the Committee’s request,” Mnuchin wrote in a one-page letter to Neal in his initial May 6 refusal. Mnuchin added that he had discussed the request with the Department of Justice, which said it couldn’t lawfully furnish Trump tax returns due to possible privacy violations.

But now that Mnuchin has made it clear he has no intention of handing over the returns, the fight is just getting started. There was some speculation that Neal would go directly to court because the Trump administration is aggressively fighting other subpoenas Democrats have issued. He will probably still have to do that, but by going through the subpoena process yet again, Democrats are establishing a paper trail to build a stronger case when they ultimately end up in front of a judge.

According to CNN, Neal told reporters in April he “wanted to make sure that the case we constructed was one that stood up under the critical scrutiny of the courts.”

Trump officials have been obstinate on tax returns from the beginning. Acting White House Chief of Staff Mick Mulvaney in an April interview with Fox News Sunday called the Democrats’ request a “political stunt” and said they would “never” see Trump’s returns. “They know they’re not going to get this,” he said.

In other words, the fight over Trump’s tax returns is going to last for a while.

Democrats used a 1920s law to make this request

Democrats invoked Section 6103 of the Internal Revenue Code, a statute dating back to 1924, which authorizes the Ways and Means Committee to request from the Treasury Department the tax return information — personal or business — of any taxpayer. Treasury, theoretically, has to comply, and since it hasn’t, that’s where the legal battle would likely come in.

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

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.

Congress made some changes to the law in 1976, including eliminating the ability of the president and any congressional committees not related to tax to disclose tax information to the public. But a handful of tax committees, including Ways and Means, can still lawfully request someone’s tax returns.

Democrats have been building their case for a while

Democrats will have a better shot in succeeding in getting Trump’s tax returns if they can build a strong case for why they want them and show that they’re pursuing them out of legislative and oversight duties, not as part of a partisan fishing expedition.

Neal in an April 3 statement on his request laid out the Democrats’ argument. He said the Ways and Means committee has the responsibility to conduct oversight of the federal tax system and “determine how Americans — including those elected to our highest office — are complying with those laws.” He also said the committee needs to make sure the IRS is doing its duty in properly enforcing tax laws. The IRS has a policy of auditing all presidents and vice presidents, and Democrats want to make sure that’s what they’re doing.

Rep. Bill Pascrell (D-NJ), who has been making the case for pursuing Trump’s tax returns under Section 6103 basically since Trump was inaugurated, in an emailed statement earlier this year said he believed evidence indicating the president “has abused our tax laws is plentiful.” 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 said. “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.”

The White House has no interest in complying

Even before Democrats put in their formal request for the president’s tax returns, the signal from the Trump administration was they were not interested in cooperating.

Mnuchin in testimony before the House of Representatives in March suggested he would seek to keep Trump’s tax returns under wraps. “We will follow the law and we will protect the president as we would protect any individual taxpayer under their rights,” he said.

William Consovoy, Trump’s personal lawyer, sent a letter to Treasury Department general counsel Brent McIntosh arguing against releasing Trump’s tax returns. He said that the tax code “zealously guards taxpayer privacy” and that Neal’s request “flouts … fundamental constitutional constraints.”

He said the Ways and Means Committee has “no legitimate purpose” for requesting Trump’s tax returns, and even if it did, it doesn’t matter. “Even if Ways and Means had a legitimate committee purpose for requesting the President’s tax returns and information, that purpose is not driving Chairman Neal’s request,” Consovoy wrote. “His request is a transparent effort by one political party to harass an official from the other party because they dislike his politics and his speech.”

Jay Sekulow, another personal attorney for Trump, in an appearance on ABC’s This Week a few days after Neal’s original letter, also dismissed the Democrats’ request.

“This idea that you can use the IRS as a political weapon, which is what is happening here, is incorrect both as a matter of statutory law and constitutionally. We should not be in a situation where individual’s — individual private tax returns are used for political purposes,” he said. He also said that the president hasn’t asked for House Speaker Nancy Pelosi’s tax returns.

President Trump's attorney Jay Sekulow says "if necessary," the fight over Trump releasing his tax returns "will be litigated."



"We should not be in a situation where ... individual private tax returns are used for political purposes," he adds https://t.co/a2Vie2FVgM pic.twitter.com/3YMIrSTzij — ABC News (@ABC) April 7, 2019

As the New York Times notes, Trump’s lawyers’ thoughts on the issue don’t really make much of a difference one way or the other, but they’re indicative of the Trump team’s stance on the issue.

Democrats getting Trump’s tax returns doesn’t necessarily mean we’ll get to see them

Even if Democrats are able to get the president’s tax returns, there is debate over whether they can legally be made public.

Even if the Ways and Means Committee gets Trump’s tax returns the easy way, it could then vote to have some or all of the tax returns released to the rest of the House of Representatives, so all members would have access to it. But then it’s unclear if it’s legal to make that information public. Now they would have to go through a lengthy court battle even before they get to that step.

Ken Kies, the managing director of the Federal Policy Group, testified before Congress in February 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 argued that, if the committee votes to release them to the full House, making the tax returns public would be allowed.

That debate — and the conclusion to it — is still a long way away. This fight is going to play out for quite some time.

The news moves fast. Catch up at the end of the day: Subscribe to Today, Explained, Vox’s daily news podcast, or sign up for our evening email newsletter, Vox Sentences.