37 CFR 1.913 : Patents, Trademarks, And Copyrights (§ 1.1 To Chapter V) — (§ 1.1 To Chapter V) — United States Patent And Trademark Office, Department Of Commerce (§ 1.1 To Parts 151-199) — General (§ 1.1 To §§ 5.31-5.33) — Rules Of Practice In Patent Cases (§ 1.1 To § 1.1071) — Inter Partes Reexamination Of Patents That Issued From An Original Application Filed In The United States On Or After November 29, 1999 (§ 1.902 To § 1.997) — Requirements For Inter Partes Reexamination Proceedings (§ 1.903 To § 1.927) — Persons eligible to file, and time for filing, a request for inter partes reexamination.

(a) Except as provided for in § 1.907 and in paragraph (b) of this section, any person other than the patent owner or its privies may, at any time during the period of enforceability of a patent which issued from an original application filed in the United States on or after November 29, 1999, file a request for inter partes reexamination by the Office of any claim of the patent on the basis of prior art patents or printed publications cited under § 1.501.

(b) Any request for an inter partes reexamination submitted on or after September 16, 2012, will not be accorded a filing date, and any such request will not be granted.