Here’s a pro tip for lawyers: if you are going to ask a court to fundamentally alter the balance of power between the legislative branch and the judiciary, it’s a good idea to accurately describe any Supreme Court cases you rely upon. It’s a bad idea to tell the court that a case that absolutely eviscerates your legal argument is the best thing you have going for you.

Earlier this month, two House committees issued subpoenas asking two banks to turn over financial records concerning President Donald Trump, his businesses, and his immediate family that helps run those businesses. At least one of these banks, Deutsche Bank, says it will comply with these subpoenas on Monday unless a court orders them not to.

So, of course, Trump sued, seeking just such a court order. The case is Trump v. Deutsche Bank.

Trump’s lawyers make two arguments, neither of which should prevent Congress from obtaining the information it seeks. The first is that Congress did not comply with procedures outlined by the Right to Financial Privacy Act — a plausible claim, but ultimately one without much force because the House could cure any violation by simply following those procedures.

The more potent claim is that the subpoenas exceed Congress’ lawful authority because the House lacks “a legitimate legislative purpose” for seeking the financial information it requested. To support this claim, Trump’s lawyers primarily rely on a 1975 Supreme Court case called Eastland v. U.S. Servicemen’s Fund.

It is true that, in a footnote, Eastland does say that when Congress seeks information from one source about a third party, “a court may inquire to determine whether a legitimate legislative purpose is present.” But virtually everything else in the Eastland opinion cuts against Trump’s legal position — and it cuts hard.

Eastland involved what was almost certainly a harassment campaign against a non-profit organization perceived to be insufficiently supportive of the Vietnam War. The “Eastland” in this case was Sen. James Eastland (D-MS), an arch-segregationist who chaired the Senate Subcommittee on Internal Security. The defendant was a nonprofit organization that allegedly published newspapers and set up “coffeehouses” for servicemembers that became a “focus of dissent and expressions of opposition within the military toward the war in [Southeast Asia].”

Eastland sought this nonprofit’s financial records from its bank.

Yet, despite the deeply troubling First Amendment implications of Eastland’s investigation, the Supreme Court held that the courts should not intervene. “We conclude that the actions of the Senate Subcommittee, the individual Senators, and the Chief Counsel are protected by the Speech or Debate Clause of the Constitution,” Eastland held, adding that the subpoenas “are therefore immune from judicial interference.”

The court explained that “once it is determined that Members are acting within the ‘legitimate legislative sphere’ the Speech or Debate Clause is an absolute bar to interference.”

Trump argues that the subpoenas seeking his financial records are not within the legitimate legislative sphere because they “seek to investigate events that could not possibly lead to legislation within the Intelligence or Financial Services Committees’ statutory jurisdiction and constitutional authority.” But that’s not the appropriate legal standard. The question isn’t whether Trump’s financial records will themselves reveal information that will lead to congressional legislation, the question is whether those records might inform the legislative process more generally — and there’s really no question that they do.

As House Financial Services Committee Chair Maxine Waters explained, the records seek to investigate “potential use of the U.S. financial system for illicit purposes” — and they seek to investigate such alleged illicit use of the U.S. financial system by the President of the United States.

Investigating the president’s alleged illegal actions is within the legislative sphere. The president is a key player in the legislative process. He may propose legislation and veto it. As head of the Executive Branch, the president shapes what kind of information Congress receives and much of what they know about how the government is functioning. If the president is secretly motivated by illegal financial dealings — or by a desire to protect his criminal conspirators — that is absolutely a matter of legislative concern that Congress should be aware of in its negotiations with the president.

As Eastland explains, “the power to investigate is inherent in the power to make laws because ‘[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.'”

Legislation aside, there’s also another compelling reason why Congress would validly investigate the President of the United States.

The Constitution gives the House “the sole power of impeachment.” And, just as a Congress cannot legislate wisely or effectively without the information gleaned from investigations, it also cannot determine whether a federal official is worthy of impeachment without the power to investigate that officials allegedly illegal actions. The power to investigate the president is inherent in the power of impeachment.

So that’s what the law says. But, of course, any analysis of a lawsuit involving Donald Trump must come with a caveat. The Constitution is also pretty damn clear that the government may not single out people of a particular faith for inferior treatment, but that did not stop this Supreme Court from upholding Trump’s Muslim ban.

There is always a risk, no matter how clear the law may be, that this Supreme Court will ignore it.

But Trump’s only hope of prevailing in the Deutsche Bank case is to pray for judicial lawlessness. Even the very case Trump relies upon in his legal complaint makes it quite clear that he should lose.