The U.S. Court of Appeals for the Federal Circuit sounded dubious Monday about Allergan’s bid to use Native American tribal immunity as a shield from administrative patent review.

Judges Timothy Dyk and Jimmie Reyna fired a volley of skeptical questions at Jonathan Massey, an attorney representing Allergan Inc. and the Saint Regis Mohawk Tribe during an hour-long argument. Allergan and the tribe entered into a licensing agreement last summer aimed at terminating inter partes review of Allergan’s Restasis patents.