The procedures by which the Patent Trial and Appeal Board (PTAB) has routinely conducted inter partes reviews (IPRs) have been dealt another blow. On March 18, the Federal Circuit ruled that the clear and unambiguous language of the governing statute—35 USC Section 315(c)—does not authorize the Board to “join” an entity to an IPR proceeding in which it is already a party (“same-party joinder”) or to “join” new issues “material to patentability, such as new claims or new grounds” to an existing IPR. The decision arose after Windy City Innovations, LLC appealed to the Federal Circuit a set of final written decisions in six IPRs triggered by Facebook against four patents that Windy City had asserted against it in district court litigation. That case is also on appeal after District Judge Yvonne Gonzalez Rogers invalidated the surviving claims from one of the same four patents under Alice, but the Federal Circuit’s decision may breathe new life into Windy City’s litigation—and is likely to bring sweeping changes to the manner in which the PTAB adjudicates IPRs.