A bipartisan group of former House lawyers are backing the House Ways and Means Committee's lawsuit seeking President Donald Trump's federal tax returns, warning a ruling that lawmakers can't go to court to enforce their subpoenas could significantly damage Congress' oversight authorities.

In an amicus brief filed in the case at the District Court for the District of Columbia on Friday, the former House counsels challenge Trump's legal claims that the House lacks standing to bring forward the case.

"The primary question that this brief addresses—whether the entity that issued the subpoena has standing to enforce it—is equally basic. Of course it does. How could it not?" the brief reads.

Former House general counsels Kerry Kircher, Irvin Nathan, Geraldine Gennet and Thomas Spulak are all on the brief, as are former acting House general counsels William Pittard and Charles Tiefer.

Robbins, Russell, Englert, Orseck & Untereiner attorneys Lawrence Robbins, Wendy Liu and Hunter Smith filed notices of appearances for the ex-House attorneys.

The brief urges U.S. District Judge Trevor McFadden of the District of Columbia to dismiss Trump's arguments that past rulings allowing Congress to go to court to enforce subpoenas were incorrectly decided and that the typical process used to share documents between the two branches should be allowed to play out.

"In these circumstances, judicial abstention would not just hand the Executive a victory in its effort to resist this subpoena, but also disturb the functioning of Congressional oversight more generally," the filing states.

The former House attorneys pointed to Trump administration officials' assertions that the lawmakers would "never" get the tax returns, after the documents were requested under a federal statute that states the IRS "shall" hand over the returns to the committee when requested.

Treasury Secretary Steven Mnuchin denied the request, claiming the lawmakers lacked a "legitimate legislative purpose." And he gave the same reasoning in rejecting a subpoena issued by the committee for the returns.

The former House lawyers said that when executive branch officials fail to comply with subpoenas, a committee can either file a civil suit to enforce the subpoena or vote to refer the officials for criminal prosecution. But charges are rarely pursued in criminal contempt cases, as that decision is made at the discretion of the Justice Department.

They also rejected the possibility that Congress could hold officials in inherent contempt to comply with a subpoena, saying "that power exists today more in theory, than in reality." And they said that other forms of leverage, like denying funding requests from federal agencies, aren't sufficient enough to address the harm done by noncompliance with a subpoena.

The attorneys said that when courts have ruled on whether the House can go to court to enforce subpoenas, "both times it reached the obvious answer: Yes."

"Indeed, Defendants all but concede that every court to address the issue has held that houses of Congress, and their committees, have standing to enforce subpoenas. Their efforts to persuade this Court to become the first to hold the contrary are without merit," the brief reads.

The House lawyers also rejected Trump's argument that the full House must authorize the lawsuit, noting that the chamber's rules state that is not the case.

And they further came out against the claim that the courts shouldn't be involved in a dispute between two other branches of the federal government: "Declining to exercise jurisdiction under these circumstances would upset, rather than restore, the balance of power among co-equal branches."

The lawyers even pointed to a prior ruling from McFadden himself, in which he wrote that "informational injuries to Congress arise primarily in subpoena enforcement cases." 

"The stakes here are not just the Executive's failure to comply with a single Congressional subpoena, but the much broader calibration of inter-Branch relations," the brief states. 

"Far from respecting the Constitution's carefully crafted separation of powers, declining to enforce the Committee's subpoena would grant the Executive the unbridled authority to evade Congressional oversight," the House attorneys concluded.

Justice Department lawyers and Trump's private attorneys at Consovoy McCarthy argued in a joint filing earlier this month that McFadden should dismiss the House lawsuit because the committee can't "conscript the Judiciary on its side of a dispute with the Executive Branch over a congressional demand for information."

McFadden ruled in June that the House did not have standing to sue the Trump administration over the diversion of military funds for a border wall. But he noted in that opinion, as highlighted in Friday's amicus brief, that lawmakers could go to court to enforce subpoenas.

"Indeed, using the Judiciary to vindicate the House's investigatory power is constitutionally distinct from seeking Article III standing for a supposed harm to Congress's Appropriations power," the judge, a Trump appointee, wrote in the opinion. "Unlike the Appropriations power, which requires bicameralism and presentment, the investigatory power is one of the few under the Constitution that each House of Congress may exercise individually."

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