Joinder may allow a party to challenge patent claims with an IPR even if the one-year time bar in Section 315(b) would otherwise preclude the party from filing a petition for IPR. In Uniloc 2017 LLC v. Facebook Inc., Nos. 19-1688, -1689 (Fed. Cir. 2021), the Federal Circuit resolved whether the joining party can continue the challenge even if the original petitioner no longer can due to estoppel.