Estoppel Remains Malleable

A few months ago, in BTG International Ltd. v. Amneal Pharmaceuticals LLC, the Federal Circuit invited the Patent Office's views on the scope of the petitioner estoppel under 35 U.S.C. § 315(e)(2). We noted then that this is an estoppel a district court may apply, but the Patent Office may not. In response to the court's invitation, the Patent Office said that a court may apply this statutory estoppel not only to petitioners who lose an IPR, but also to those who prevail. The Office conceded that estopping prevailing IPR petitioners "leads to the counterintuitive result that a district court would not be able to consider invalidity arguments that the Board found persuasive." But the Office said that this will have no practical effect in most cases. If the Federal Circuit vacates or otherwise reverses the Board's final written decision, then estoppel indisputably attaches; and if the court affirms, then the challenged claims will forever be canceled and unenforceable.