In the inter partes review (IPR) proceeding between Mylan Pharmaceuticals, Inc. v. Allergan, Inc., before the Patent Trial and Appeal Board (PTAB), counsel representing the Patent Owner raised a defense that, if successful, could circumvent IPR proceedings and shield patents from post-grant review. Allergan, whose patents for the drug Restasis which are the subject of the IPR proceeding challenging their validity, recently struck a deal with the St. Regis Mohawk Tribe, transferring its patent rights in exchange for a license. Last week, counsel representing the Tribe, a sovereign nation, raised the defense of sovereign immunity, arguing its immunity places the patents at issue beyond the PTAB’s authority. The Tribe has until September 22 to file its brief on the immunity defense.