35 U.S.C. § 315 — Relation to other proceedings or actions

(a) Infringer's civil action. (1) An inter partes review cannot be started if, before the review petition is filed, the petitioner (or the real party in interest) already filed a civil lawsuit challenging the validity of a claim in that patent. (2) But if the petitioner or real party in interest files that kind of lawsuit on or after the date they filed the review petition, the lawsuit is automatically paused. It stays paused until one of three things happens: (A) the patent owner asks the court to lift the pause; (B) the patent owner files a lawsuit or counterclaim accusing the petitioner or real party in interest of infringing the patent; or (C) the petitioner or real party in interest asks the court to dismiss the lawsuit. (3) A counterclaim that challenges a patent claim's validity does not count as a "civil action" for purposes of this subsection. (b) Patent owner's action. An inter partes review cannot be started if the petition is filed more than one year after the petitioner, the real party in interest, or someone in privity with the petitioner was served with a complaint alleging they infringed the patent. That one-year deadline does not apply to a request to join an existing review under subsection (c). (c) Joinder. If the Director starts an inter partes review, the Director may, at their discretion, let another person join that review as a party. That person must have properly filed their own petition under section 311, and the Director must decide — after getting a preliminary response under section 313, or after the time to file one runs out — that this second petition also deserves review under section 314. (d) Multiple proceedings. Despite what sections 135(a), 251, and 252, and chapter 30 say, if another proceeding about the same patent is also before the Patent Office while the review is pending, the Director may decide how both the review and the other proceeding should move forward — including staying, transferring, combining, or ending either one. (e) Estoppel. (1) If a petitioner's inter partes review of a patent claim ends in a final written decision under section 318(a), then that petitioner — or the real party in interest or someone in privity with them — cannot later ask the Patent Office to reconsider that same claim on any ground they raised, or reasonably could have raised, during the review. (2) The same petitioner, real party in interest, or privy also cannot argue, in a federal court case under section 1338 of title 28 or in an International Trade Commission case under section 337 of the Tariff Act of 1930, that the claim is invalid on any ground they raised or reasonably could have raised during the review.