Code of Federal Regulations Title 37. Patents, Trademarks, and Copyrights § 37.42.101 Who may petition for inter partes review

(a) Before the date on which the petition for review is filed, the petitioner or real party-in-interest filed a civil action challenging the validity of a claim of the patent;

(b) The petition requesting the proceeding is filed more than one year after the date on which the petitioner, the petitioner's real party-in-interest, or a privy of the petitioner is served with a complaint alleging infringement of the patent;  or

(c) The petitioner, the petitioner's real party-in-interest, or a privy of the petitioner is estopped from challenging the claims on the grounds identified in the petition.