37 CFR § 1.176 - Examination of reissue.
(a) A reissue application will be examined in the same manner as a non-reissue, non-provisional application, and will be subject to all the requirements of the rules related to non-reissue applications. Applications for reissue will be acted on by the examiner in advance of other applications.
(b) Restriction between subject matter of the original patent claims and previously unclaimed subject matter may be required (restriction involving only subject matter of the original patent claims will not be required). If restriction is required, the subject matter of the original patent claims will be held to be constructively elected unless a disclaimer of all the patent claims is filed in the reissue application, which disclaimer cannot be withdrawn by applicant.