The Justice Department is getting involved in President Trump’s lawsuit seeking to block the Manhattan district attorney’s subpoena of his tax records from his private accounting firm. Is it out of line?

Not really. Or at least not yet.

The action — which came in a filing called a “statement of interest” — is certainly eyebrow-raising in as much as it commits the federal government’s resources to what is on one level just an ordinary subpoena battle. And critics will be quick to see a suggestion of the improper yoking of the Justice Department to the president personally, as opposed to the office of the presidency.

The suit here is relatively pedestrian. It is noteworthy in that Trump chose to bring a separate action (in his private capacity) against the district attorney (in his official capacity) in federal court rather than move to quash the subpoena in the underlying state court case. It is further noteworthy in that Trump’s argument — that a local prosecutor may not even investigate a sitting president — is aggressive and likely to fail. Trump argues that the Constitution precludes subjecting a sitting president to any aspect of the state criminal process, including the subpoena of his accountants.

Recall that special counsel Robert S. Mueller III, in standing down from assessing the bottom-line criminality of the president’s conduct in relation to the Russia probe, was emphatic in affirming the prosecutorial power to investigate Trump. That power, in fact, seems critical in light of the department’s determination overall that a sitting president cannot be indicted — the prosecution has to be able to gather evidence of possible criminality for use after a president’s tenure.

The legal arguments in the department’s statement of interest — which lists the Justice Department’s Civil Division in Washington and the office of the U.S. attorney for the Southern District of New York — are arcane and procedural. They counter the district attorney’s procedural arguments for dismissing Trump’s lawsuit.

In brief, the department argues that there is an express statutory basis for the president’s lawsuit that overrides the general principle that federal courts should not enjoin pending state criminal proceedings.

Second, the department contends that a court-created doctrine of abstaining from wading into state-law criminal disputes — known as “Younger abstention” — similarly doesn’t apply here given the weighty constitutional questions that Trump’s case might present under Article II and the supremacy clause.

Reportedly there is consternation in the Southern District of New York at that venerable office’s link to a Trump-friendly filing. And it is perhaps telling that, contrary to normal practice, no line prosecutor from the office is listed on the brief.

But all the department has really done in the filing is argue the federal court is the right place to resolve Trump’s constitutional arguments.

Still, it is clear that the department, if permitted, intends to file a brief on behalf of Trump and potentially embrace an argument that a local prosecutor cannot even investigate a president.

That eventual filing will be the real litmus test of the department’s conduct here. It is entirely possible, for example, that the department will argue that a president cannot be indicted, but won’t go so far as to push the essentially royalist position that the president cannot even be investigated. We will have to wait and see.

In the meantime, the department’s underlying rationale for inserting itself into the case — that the “unique character of the President’s office and his responsibilities in the Nation’s constitutional structure” require the federal court to exercise jurisdiction — is defensible. Given the president’s singular responsibilities, it is difficult to disentangle the office from the person who occupies it. It is more than foreseeable that the court’s resolution of this case could have important implications for the office of the presidency. That is part of the reason we have federal courts.

The department’s recent track record gives pause as to whether it can be counted on to advance and defend the right constitutional position even where it might undermine Trump’s personal political interests. But it’s the next filing, not this one, that really matters.

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