Robert Bauer, professor of practice at New York University School of Law, served as White House counsel to President Barack Obama.

President Trump has been sued for allegedly violating the Constitution’s emoluments clause, which raises the question: Who should represent him? As it stands now, because the president has been sued in his official capacity, the Justice Department will appear for the defense on behalf of the United States. But in an unprecedented case involving the president’s extensive private business interests and its management through a controversial “trust” arrangement, that is the wrong choice.

Instead, the president should be required to retain private counsel to represent him. The Justice Department should express its view separately but also independently of the department’s senior appointed leadership. This arrangement would make it more likely that the Justice Department will advance a constitutional position in the broader public interest, not just in the narrow service of a president who happens to be in office at the moment.

The lawsuit filed in federal court in Manhattan alleges violations of two separate limitations on the receipt of “emoluments.” One, involving the foreign emoluments clause, asserts that foreign governments are directly or indirectly patronizing Trump’s hotels, leasing his properties and helping his businesses profit. The second involves a parallel clause prohibiting the receipt of emoluments, beyond the president’s salary, from individual states or the federal government. Recently, new plaintiffs joined the suit to argue that this amalgam of public responsibility and private holdings subjects other U.S. businesses to unfair competition.

Requiring a clear separation of the president’s business interests from those of the United States does not prejudice Trump’s defense on the merits. He can and will make his case. Neither the scope nor the application of these provisions is clearly settled. Some scholars argue that the foreign emoluments clause reaches only payment for official services rendered. There is also disagreement about whether the prohibition on emoluments applies to “arm’s-length” business transactions with companies in which the president may have an interest.

Complicating these questions are sharp differences on the question of whether the president’s trust arrangement, run by his sons, adequately insulates him from direct engagement with his business while in office. The president, who remains free to draw income from the trust, insists that it does. The director of the Office of Government Ethics publicly disagreed.

At the same time, there is little doubt that the president’s business interests are active and enhanced by the connection to state power. One of his sons has pronounced the Trump brand to be “the hottest it has ever been” and has said that his father would receive regular, probably quarterly, reports on his business’s profitability.

It is precisely these unique features of the case — new constitutional law to be made on these exceptional facts — that suggest why Justice Department senior leadership chosen by the president should not direct the defense of this lawsuit. After all, their boss has asserted repeatedly that he has observed all constitutional and ethical requirements. No one can reasonably assume that department appointees are unaware of the stakes for their leader. They must now develop a constitutional position free of any suggestion that it is responsive to the chief executive’s personal concerns.

The politics of the situation only add to the pressure on the department. What would it mean for the president, politically and personally, if the department’s defense departed in meaningful particulars from the strong endorsement of Trump’s position already tendered by his private legal team?

Private lawyers for Trump are most appropriately situated to provide a defense protective of Trump’s personal business interests. These lawyers established, and then publicly defended, his trust arrangement. They also structured the procedures for monitoring and addressing conflicts of interest and are responsible for administering them.

The position of the U.S. government will require attention and representation. The courts will expect to hear the Justice Department’s views, which presents another challenge. Its participation cannot consist, or appear to consist, of echoing the president’s private defense, under the watchful eye of its presidentially appointed leadership. It can address this problem by appointing well-respected special counsel to develop and argue a position on behalf of the public. Or it can make — and of critical importance, disclose — internal arrangements to allow career lawyers within the Office of Legal Counsel and the Office of the Solicitor General to present the position of the United States in a friend-of-the-court brief.

By having the president and the department go their separate ways, the basic proposition will have been laid down: In this extraordinary case, the government’s business and the president’s are not the same.