The U.S. Court of Appeals for the Federal Circuit has stepped into the debate over tribal sovereign immunity at the Patent Trial and Appeal Board.

The D.C.-based appellate court on Wednesday stopped a PTAB proceeding in which the board has declined to recognize the Saint Regis Mohawk Tribe’s sovereign immunity. The Federal Circuit scheduled a June hearing on the tribe’s bid to dismiss the proceedings, in which generic pharmaceutical companies challenge the validity of patents on Allergan’s Restasis dry eye medication.