37 CFR 1.913: 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.