As Democrats edge closer to taking control of the U.S. House, many of the party’s supporters are wondering what, if anything, the new House majority can do to obtain and make public President Donald Trump’s tax returns.

Breaking with tradition, Trump has consistently refused to release his returns, something that every previous presidential nominee and president had done voluntarily for decades. Critics of the president say his returns could shed light on possible conflicts of interest and irregularities in his holdings.

We checked with several experts to gauge the state of the law governing such releases, as well as the outlook for possible public release.

How can the House secure an individual’s tax returns?

Attention has focused on a provision of the law known as 26 U.S. Code § 6103. This allows the chairman of the tax-writing House Ways and Means Committee, among other senior lawmakers, to seek returns by sending a written request to the Treasury Secretary. Officially, the decision to release the returns would be made by the Treasury Secretary, not the White House, although it’s not difficult to imagine presidential pressure being exerted on the secretary to refuse.

This legal authority is almost a century old, said University of Virginia law professor George Yin. "Congress decided that tax information should remain confidential except in two situations," Yin has written. "First, it authorized the president to determine whether any tax information could be disclosed. And, in 1924, it gave the same power to certain congressional committees." After Watergate, the presidential power was rescinded, but the congressional power remains.

Is a request for Trump’s returns expected to be made once the Democrats take control of the House?

Yes. The lawmaker who’s in line to chair Ways and Means, Rep. Richard Neal, D-Mass., has said publicly that he plans to do so. "I think we would all be comfortable if this was done on a voluntary basis," Neal told CNN. "If they would resist the overture then I think you could probably see a long and grinding court case," he added.

Once they’re obtained, what can lawmakers do with the returns?

According to the same provision of the law, any return or any information from a return "may be submitted by the committee to the Senate or the House of Representatives, or to both." Once in the hands of rank and file lawmakers, it would be hard to stop the returns -- perhaps with some redactions -- from reaching the public. The reason: Under Article 1, Section 6 of the Constitution, known as the "speech or debate" clause, lawmakers are exempt from executive or judicial branch consequences -- such as criminal and civil penalties -- for "legislative acts" made as part of their official responsibilities.

Can Treasury Steve Mnuchin refuse the request?

He can try.

"The law has rarely been exercised, but when it has come up, to my knowledge, there has not been any controversy about compliance with the congressional request," Yin told PolitiFact. "The statute does not provide any grounds to refuse. So if the Treasury Secretary refuses the congressional request, we are largely in new territory."

If Mnuchin does refuse, then Congress can hold him in contempt. Then, House Democrats could escalate to a subpoena. If Mnuchin refuses again, "that’s when it hops into court," said Andy Grewal, a University of Iowa law professor. The court case could then climb the judicial ladder, perhaps ultimately reaching the Supreme Court. "It may not necessarily be resolved in two years" -- the time Trump has left in his current term.

Jeff Hoopes, an assistant professor of accounting at the University of North Carolina’s Kenan-Flagler School of Business, said that because the facts in the Trump case are new, "we really are in somewhat uncharted territory. They may well have the power, but I don’t think anyone really knows how it will work out."

For the record, Mnuchin told the New York Times in October that "if they win the House and there is a request, we will work with our general counsel and the IRS general counsel on any requests."

What arguments could the administration make to quash the request?

Legal scholars suggest that the case, if it materializes, may hinge on whether the request is considered to be for a legitimate congressional purpose or whether it’s just a ploy to embarrass the president.

"Everybody agrees that whatever the tax code might say, Congress has to have a legitimate purpose for an inquiry," Grewal said. "But there’s a point of contention about whether there would be a legitimate purpose for such a request in this case."

Grewal said he’s sympathetic to the notion that the IRS deserves deference, given that, by Trump’s own acknowledgement, it has audited his returns for many years running.

Other scholars view this argument as a red herring, countering that Congress has a legitimate interest in executive branch oversight.

"Such a step is appropriate and necessary, as part of our checks and balances," Steve Rosenthal, a senior fellow in the Urban Institute-Brookings Institution Tax Policy Center, has written. "The Constitution calls upon the House, along with the Senate, both to enact legislation and to oversee whether those laws are faithfully executed. To fulfill its oversight responsibility, I believe the House should demand the president’s tax returns."

Beyond ordinary oversight powers, two elements could make the justification for demanding Trump’s returns even stronger, legal experts say.

One strategy would be to limit the request to tax returns filed during Trump’s presidency -- when Trump, in theory, could have influenced the IRS from above.

There’s historical precedent for this. According to the tax publication Tax Analysts, President Richard Nixon during Watergate faced "allegations — eventually included in one of the articles of impeachment against him — that the president attempted to use the IRS for unlawful purposes." In response, the congressional Joint Committee on Taxation -- another committee with the authority to demand tax returns -- approved the release of the president’s tax returns for 1969 through 1972. That move was made on a 9 to 1 vote, with three Republicans joining six Democrats.

The second strategy is to wait for Special Counsel Robert Mueller to release his report to Congress on Russian interference in the 2016 election. If Mueller’s report includes references to material from Trump’s returns -- which, as a law enforcement officer, he almost certainly has access to -- then Congress would have a strong argument for demanding a look themselves as a way of vetting Mueller’s conclusions.

"Once you have a hook, whether through Mueller or otherwise, then I think the case for Congressional double-checking is much stronger," Grewal said.

Even without these two approaches, though, Rosenthal told PolitiFact that he thinks Congress’ oversight responsibilities should be sufficient to justify a release. "I don’t think having a legitimate purpose is a very high bar" to meet in the case of Trump’s tax returns, he said.

What precedents could be used to argue in favor of releasing Trump’s returns?

One is the Watergate example above. Another is the impetus for passing the law in the 1920s -- a series of scandals in President Warren G. Harding’s administration, which included Teapot Dome. That involved bribes for oil leases, as well as conflict-of-interest allegations against Treasury Secretary Andrew Mellon, who continued to operate businesses while serving in the cabinet.

"The parallels to President Trump (to Mellon) are striking," Rosenthal has written. "Trump maintains a sprawling business empire, which he refuses to transfer to a blind trust." This and other concerns "raise legitimate questions about whether the president is running the government for his benefit or the public’s—or both. Is he profiting from his position? Is the public harmed? Is the IRS auditing the president’s returns appropriately and without favoritism? Has the IRS proposed any adjustments, and has the president paid them?"

Is there any legislation on tap that could affect this issue?

Yes. In August, Sen. Elizabeth Warren, D-Mass., proposed the Anti-Corruption and Public Integrity Act, which would require the IRS to release eight years of returns for presidential and vice presidential candidates and two years for congressional candidates. The law would also require returns to be disclosed for businesses and nonprofit groups owned or operated by federal candidates. (Warren has voluntarily disclosed 10 years of her own returns.)

The legislation, which would need to be reintroduced in the new Congress, would end the existing system, by which all presidents and presidential candidates in the post-Watergate period released their tax returns by custom but not by law.