Is President Donald Trump legally entitled to withhold his tax returns from the House Committee on Ways and Means?

Probably not — but it's not simple.

The governing legal text, known as section 6103, is buried in a lengthy set of provisions governing confidentiality and disclosure of tax returns. It says this:

Upon written request from the chairman of the Committee on Ways and Means of the House of Representatives, the chairman of the Committee on Finance of the Senate, or the chairman of the Joint Committee on Taxation, the Secretary (of Treasury) shall furnish such committee with any return or return information specified in such request, except that any return or return information which can be associated with, or otherwise identify, directly or indirectly, a particular taxpayer shall be furnished to such committee only when sitting in closed executive session unless such taxpayer otherwise consents in writing to such disclosure.

Rep. Richard Neal, chairman of the Ways and Means Committee, invoked section 6103 on April 3, when he asked for Trump's federal income tax returns for 2013 through 2018 — along with the returns for eight organizations owned by or associated with Trump.

At first glance, section 6103 authorizes Neal to get those returns. It does not contain any exceptions. It does not give taxpayers, including the president, a right of refusal.

Why is there any issue here?

In declining Neal's request on May 6, Treasury Secretary Steven Mnuchin offered a brief answer. He said that the provision quoted above "is bounded by Congress's authority under the Constitution, and the Supreme Court has held that the Constitution requires that Congressional information demands must reasonably serve a legitimate legislative purpose." The president's personal lawyer, William Consovoy, elaborated on this point in detail.

On that general proposition, Mnuchin and Consovoy are certainly right. Notwithstanding the broad language of section 6103, both the Supreme Court and lower courts have made it clear that when congressional committees are seeking information, they have to have a valid purpose.

It follows that the House Ways and Means chairman cannot ask for the tax returns of individuals or groups solely because he dislikes their political convictions. Nor can he target you and your family, if his goal is to harass and embarrass you.

Neal was obviously advised of that fact. In his letter, he identifies a legitimate legislative purpose: "the Committee is considering legislative proposals and conducting oversight related to our Federal tax laws, including, but not limited to, the extent to which the IRS audits and enforces the Federal tax laws against a president."

He added: "we do not know what the IRS is reviewing, whether the IRS review includes audits that were ongoing before he took office, or even if a mandatory examination actually is taking place." In other words, Neal's goal is to see whether the Internal Revenue Service is giving favorable treatment to the president.

That sounds reasonable enough. But the White House might be forgiven if it is thinking: Really? Is Neal asking for Trump's tax returns because he wants to see if the IRS is treating him favorably?

Consovoy thinks that's nuts. In his view, Neal's "request is a transparent effort by one political party to harass an official from the other party because they dislike his politics and speech."

It probably would have been smarter for Neal to say that the committee is interested in current legislative proposals to require presidential candidates to disclose their tax returns. If Trump's returns show red flags of any kind — if they offer important information that reasonably bear on voters' decisions — then the argument in favor of those proposals would seem to be strengthened.

So here's where we are. Neal has already identified a legitimate legislative purpose — not his strongest, perhaps, but perfectly legitimate. In the past, courts have been reluctant to rule that a committee's reasons for seeking information are pretextual. In any case, Neal could easily write a letter, today or tomorrow, pointing to other legitimate purposes.

Does Trump have anything to say in response?

The answer might be signaled by Mnuchin's cryptic suggestion that Neal's request "presents serious constitutional questions."

It is one thing for a committee chairman to request the tax returns of (say) corporate executives. It seems different if the request is made of the president of the United States. Any information request, imposed by members of one branch on the head of another, might be a political ploy, rather than a good-faith effort to serve legitimate legislative purposes.

Fair enough. But in the last decades, presidents and presidential candidates have released their returns as a matter of course. In these circumstances, it is pretty tough for the president to argue that he has a constitutional right to keep his tax returns private. After all, Neal is not requesting materials arguably protected by executive privilege (such as conversations between the president and his top advisers).

The last few years have shown that it's hazardous to try to predict decisions of federal courts. But if you reread the language of section 6103, you'll probably reach a simple conclusion: With respect to Trump's tax returns, Congress clearly has the upper hand.

Cass R. Sunstein is a Bloomberg Opinion columnist. He is the author of "The Cost-Benefit Revolution" and a co-author of "Nudge: Improving Decisions About Health, Wealth and Happiness."