The issue focused on New York's highest court, the Court of Appeals for the Second Circuit, which has also come under fire in recent years for its liberal leanings.

In his brief, Donald Trump Jr. asked that the appeal be heard by a three-judge panel and added: "We should not allow our systems to be subverted by political litigants who will stop at nothing to achieve their ends."

He said he had met with representatives of Russian lawyer Natalia Veselnits