WASHINGTON — A federal appeals court delivered a setback on Friday to a lawsuit by congressional Democrats accusing President Trump of illegally benefiting from his business interests while in office, saying a lower court judge hearing the suit had not adequately considered questions about the separation of powers between the president and Congress.

The order by a three-judge panel of the United States Court of Appeals for the District of Columbia Circuit is a new sign that Mr. Trump will not be forced to produce evidence in lawsuits claiming that he has violated the anticorruption clauses of the Constitution until the novel legal questions raised in those cases are resolved.

The question of what violates the clauses has never been tested in court. Three lawsuits raising the issue have been bouncing back and forth between district courts and appeals courts, and one of the cases may eventually reach the Supreme Court. The clauses restrict the ability of federal official to accept benefits, or “emoluments,” from foreign or state governments.

The Appeals Court judges rejected a request by the government to intervene in the case on an emergency basis. Instead, they said Judge Emmet G. Sullivan of the United States District Court for the District of Columbia had erred by not allowing the Justice Department to appeal his rulings at an early stage, before evidence had been gathered.