Not known for his sense of irony, President Trump probably fails to appreciate that his arguments for beating back Congress’s subpoena of his accountant’s records are the polar opposite of arguments he has employed to justify his own conduct.

In fact, Trump’s personal complaint against House Oversight Committee Chair Elijah E. Cummings (D-Md.) is the mirror image of the arguments he advanced to defend his travel ban, which the Supreme Court upheld last year in Trump v. Hawaii.

The lawsuit Trump filed Monday morning seeking a court order to block Cummings’ subpoena to Mazars USA, an accountant for the president and Trump Organization, is as much a work of political rhetoric as a claim for legal relief. The president’s complaint begins by asserting that the Democratic Party has declared “all-out political war” on the president. It proceeds to base its case that Democrats are engaging in “a campaign of abusive investigations” on a series of quotations by Speaker Nancy Pelosi (D-Calif.) and sundry House members from news conferences and political appearances in the wake of the Democratic takeover of the House after November’s midterm elections.

Trump took the exact opposite approach in Trump v. Hawaii. There, his own statements on the campaign trail had left the strong inference that his immigration order, however dressed, was a “Muslim ban.” But Trump argued that the court needed to focus on whether the order fell within the exercise of legitimate executive authority, while discounting or ignoring his own incendiary political propaganda or engaging in psychological second-guessing of the ”real” reason for his decisions.

The challengers, meanwhile, urged that the evidence of Trump’s true motive served to establish that Trump’s order fell outside the exercise of legitimate executive authority.

The Supreme Court agreed with Trump. Chief Justice John G. Roberts Jr., writing for the court, emphasized that the issue at hand was “not whether to denounce the statements” but whether the presidential order fell within the president’s executive power. Given the president’s general authority to exclude foreign nationals from the country, the court found, it sufficed for Trump to supply “a facially legitimate and bona fide reason" for his conduct. Separation-of-powers principles generally precluded the court from analyzing whether the facially legitimate reason was the actual explanation.

Fast forward to Monday’s lawsuit. Just as the president’s power to police the borders is well established, so is Congress’s power of oversight, which the court has made clear is an adjunct of its legislative function. But now, it’s Trump who is questioning motives, averring that Congress lacks any legitimate legislative purpose because its real reason for seeking the accounting records is to harass the president and score political points for 2020.

Thus, Trump is urging the court to undertake the same kind of psychoanalysis of Congress that he insisted the court avoid in Trump v. Hawaii. And the reasoning in that case applies with full force. In fact, the very case Trump cites to argue the absence of a valid legislative purpose in his complaint against Cummings cuts sharply in the opposite direction.

In that case, Eastland vs. United States Servicemen’s Fund, the court emphasized that the issuance of a subpoena pursuant to an authorized investigation is an indispensable ingredient of lawmaking: A “legislative body cannot legislate wisely or effectively in the absence of information respecting the conditions which the legislation is intended to affect or change.”

There is no serious argument that the House lacks a legitimate and bona fide reason to demand the financial information from Trump’s accountants that Trump has gone to court to conceal. Former Trump lawyer Michael Cohen’s previous testimony suggests that the president’s financial empire is, in large part, a house of cards, propped up by exaggerated estimates of particular holdings used to secure financing.

This prospect is a legitimate subject of congressional oversight in its own right — compare it, for example, to the Whitewater investigation of investments that Bill Clinton made in Arkansas before he became president. And Trump’s complex financial web also potentially exposes him to conflicts and entanglements on several fronts; understanding that prospect falls well within the House’s legitimate investigative and oversight authority. It follows, as a matter of the same separation-of-powers principles that the court emphasized in Trump v. Hawaii, that the district court should not be peeking behind the House subpoena to provide its judgment of Cummings’s real motive.

Trump’s complaint likely suffers from the same legal infirmity that he seized on to prevail in the immigration order case. If so, what a rude surprise awaits him: The separation of powers constrains his own conduct as well as that of the other branches.

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