Mr. Chawla, in the email, said that the Trump Organization played no role in the rebate application and that his company first considered applying for it in 2015, two years before he teamed up with the Trumps. He said the Trumps and the Chawlas had agreed that any rebate — which Mississippi offers in an effort to draw tourists — would not figure into fees paid to the Trumps.

Still, if the state approves the tax rebate for the Chawlas, it could indirectly, but personally, benefit the president, who owns the family business through a trust, an arrangement that raises some constitutional concerns, critics and legal experts say.

In lawsuits filed last year, a number of lawmakers, academics and state attorneys general contended that Mr. Trump was violating the Constitution’s emoluments clauses, which essentially prohibit the president from accepting certain gifts from foreign or domestic governments. A federal judge in New York dismissed one case, while a federal judge in Maryland signaled recently that he might allow another to proceed.

“The country’s founders included the emoluments clauses as a big bright-line rule,” said Jed Shugerman, a professor at the Fordham University School of Law who helped write a legal brief in support of the plaintiffs in the emoluments litigation. Assessing the Chawlas’ application, he argued that while some state incentives are allowable, “Mississippi has discretion to give the tax rebate, and if they do award it to this hotel, then they are likely giving Trump an emolument.”

In preparation for the same brief, John Mikhail at Georgetown University Law Center studied 40 dictionaries from the founding era and concluded that the term “emolument” was almost always defined more broadly than the Trump administration has interpreted it. Still, some legal experts argue that domestic emoluments are allowable so long as Mr. Trump does not earn them from his service as president.