The revelation by ProPublica on Thursday added to the lavish gifts and travel from the Texas billionaire that Justice Clarence Thomas has not disclosed.
The justice’s relationship with Harlan Crow has raised questions about whether a friendship can be separated from politics and intensified calls for an ethics code for the justices.
In a statement released by the Supreme Court, the justice said he had followed guidance from others at the court and believed he was not required to report the trips.