Section 6103(f) of the Internal Revenue Code states that “upon written request” from the chair of the House Ways and Means Committee, the Treasury secretary “shall furnish such committee with any return or return information specified in such request.” Many observers have assumed that the word shall does all the work to compel Treasury Secretary Steven Mnuchin to turn over the returns, but that bit of text must be understood in the larger context of constitutional law and precedent. Such a request, like a subpoena, must have a “legitimate” purpose.

Conor Friedersdorf: The secret that was hiding in Trump’s taxes

On Monday, Mnuchin rejected the request from Ways and Means Chair Richard E. Neal to disclose the returns, saying that it “lacks a legitimate legislative purpose.” This dispute will head to the courts to evaluate whether a “legitimate legislative purpose” exists.

But meanwhile, the New York legislature is considering a second track. The bill passed by the Senate (which would still require the approval of the assembly and the signature of the governor to become law) would authorize the Department of Taxation and Finance to share state tax-return information with the relevant congressional committees as long as there is a “specific and legitimate legislative purpose.” Note that extra word, beyond what Mnuchin himself cited: specific. Perhaps New York legislators added this word as a compromise to allay the valid concerns of those worried about overbroad fishing expeditions and vague requests that might be pretexts for a partisan purpose.

That’s exactly the point. Americans should be wary of changing our laws too abruptly just to investigate Trump. When the last law is down, as Robert Bolt wrote, the devil may turn round on you, and where would you hide? Some curbs seem necessary, to guard against future abuses. The word specific can have several meanings, but some definitions of specify suggest a connection to the word clarify. A plausible reading is that the New York legislature added the word specific to eliminate pretextual or misleading explanations.

And let’s be honest. Is Neal seeking Trump’s tax returns because he is mainly interested in the IRS’s methods? To see whether Trump owes back taxes? It is far more likely that he wishes to know whether Trump has debts or financial ties that may compromise him, or whether he has links to money laundering. That would make the request part and parcel of an impeachment inquiry, whether or not the House makes that explicit.

David Frum: Why is Trump hiding his tax returns?

House Democrats already had good reason to formally launch an impeachment inquiry and then connect their subpoena requests and tax requests to this proceeding. A growing chorus of conservative legal commentators is floating the argument that a request for tax returns ultimately driven by partisan politics does not clear the bar of serving a “legitimate purpose,” even if the House explicitly cites other purposes. Some legal experts are making a constitutional argument that such requests violate the separation of powers, unless the House is formally pursuing impeachment. This argument would challenge most of the House subpoenas.