Congressman Richard Neal filed an official request last week for the IRS to turn over six years of President Trump's past tax returns by Apr. 10, setting the stage for a high-stakes confrontation. Morning Edition Host Joe Mathieu spoke with Northeastern Law Professor and WGBH News Legal Analyst Daniel Medwed to discuss how the battle over the president’s tax returns might play out. The transcript below has been edited for clarity.

Joe Mathieu: Let's start with the basics here. How does Congress actually get access to anyone's tax returns, let alone the president's?

Daniel Medwed: Well, here's how it works. Back in 1976, after revelations about how President Nixon used tax returns against his enemies, Congress implemented these robust taxpayer protections. It's known as Section 6103 of the Internal Revenue Code. But there's a narrow exception to those robust protections. It's Section 6103 (f), and it suggests that the chair of a powerful House committee, like Ways and Means, with oversight authority over the tax law, can file a written request to the treasury secretary and the treasury secretary "shall furnish" — that's the language — they must furnish the private taxpayer information. So as you suggested, there's a letter from Neal to Treasury Secretary Mnuchin, and he has to respond by tomorrow.

Mathieu: And this is not to be confused with a state effort in New York to get returns there. Let's talk about the Treasury Secretary Stephen Mnuchin. He's set to testify today on Capitol Hill. Democrats are expected to press him on this. But Daniel, let's say he says no [and] declines to turn over the returns. What legal arguments would support that?

Medwed: Well, I do think that's the likely outcome, given everything we've heard out of the White House and Mick Mulvaney on the Sunday talk shows this weekend. I think the Trump administration has two credible — not necessarily winnable, but credible — legal arguments. First, for a 6103 (f) request to be valid, there must be a legislative purpose for the request. It must be "in aid of the legislative function." And in structuring his letter, Neal took care to clarify that there was a legislative purpose here, namely to allow his committee to evaluate whether the IRS is properly using its audit and enforcement powers when it comes to the president. Now, Trump is undoubtedly going to push back and say that's just a fig leaf that's being put out there to shield the true purpose, in his view, which is a political purpose, to basically air his dirty financial laundry for all to see. We'll just have to see how that argument plays out.

Mathieu: So there may be a battle royale brewing here over the true purpose of this request, whether it's really designed to advance a legislative purpose. But there is another potential legal objection you're talking about.

Medwed: That's right. The second argument is based on something called the right to informational privacy. It stems from two Supreme Court cases in the 1970s, which basically set up a balancing test. For the government to get access to sensitive, confidential financial information of a taxpayer, they have to show that the public interest in the disclosure outweighs the privacy interests. So here I think Congress could cite a number of public interests: the need to identify potential conflicts of interests; the need to figure out Trump's financial dealings with Russia; the need to potentially deter corruption; the need to maintain public confidence in the office of the presidency. Trump will push back and cite his privacy interests as a taxpayer with a sophisticated financial apparatus who deserves protection. That's, sort of, his argument.

Mathieu: How about the concept of executive privilege, which is far reaching. By virtue of his status as president, [it] would mean that he'd not be forced to reveal information here. Is the administration making an executive privilege claim here, too?

Medwed: Well, we've heard a lot of noise from the administration about executive privilege already. I would consider it sort of noise pollution, given how the doctrine of executive privilege is defined. The way the courts have determined the contours of that doctrine, it says that a president should be shielded [and] protected by executive privilege for the communications and activities that he or she engages in, in the function of the presidency. That information can't be forced to be disclosed because it would essentially distract the president from his or her work. However, these tax returns would not seem to implicate the presidential function for two reasons. First, four of the six tax years in question pre-date the Trump presidency — 2013 to 2016. They have nothing to do with his work as a president. And even the two years that directly overlap with his presidency — 2017 and 2018 — I think Trump would be hard pressed to argue that they somehow implicate the presidential duty, because all of us — anyone above a minimum income threshold — we have to file tax returns. It's our private duty.