WASHINGTON — Justice Neil M. Gorsuch, President Trump’s Supreme Court appointee, is scheduled to address a conservative group at the Trump International Hotel in Washington next month, less than two weeks before the court is set to hear arguments on Mr. Trump’s travel ban.

Stephen Gillers, an expert on legal ethics at New York University, questioned the justice’s decision to speak at the hotel, which is at issue in lower-court cases challenging the constitutionality of payments to Mr. Trump’s companies.

“At this highly divisive political moment, especially as many Trump decisions are likely soon to reach the court’s docket, one just days later, a healthy respect for public confidence in the court should have led Justice Gorsuch to demur,” he said.

Justice Gorsuch declined to comment, said Kathleen L. Arberg, the Supreme Court’s public information officer.