The examination of reissue applications is covered in MPEP Chapter 1400.
35 U.S.C. 251 forbids the granting of a reissue “enlarging the scope of the claims of the original patent” unless the reissue is applied for within 2 years from the grant of the original patent (or the reissue application properly claims the benefit of a broadening reissue application filed within 2 years of the patent grant). This is an absolute bar and cannot be excused. This prohibition has been interpreted to apply to any claim which is broader in any respect than the claims of the original patent. Such claims may be rejected as being barred by 35 U.S.C. 251.
For a reissue application filed prior to September 16, 2012, 35 U.S.C. 251 permits the filing of a reissue application by the assignee of the entire interest only in cases where it does not “enlarge the scope of the claims of the original patent.” For reissue applications filed on or after September 16, 2012, the assignee of the entire interest may file the reissue application if (1) the application does not seek to enlarge the scope of the claims of the original patent, or (2) the application for the original patent was filed under 37 CFR 1.46 by the assignee of the entire interest. Such claims which do enlarge the scope may also be rejected as barred by the statute. In In re Bennett, 766 F.2d 524, 226 USPQ 413 (Fed. Cir. 1985), however, the court permitted the erroneous filing by the assignee in such a case to be corrected.
A defective reissue oath affords a ground for rejecting all the claims in the reissue application. See MPEP § 1444.
Note that a reissue application is “special” and remains so even if applicant does not make a prompt reply. See MPEP § 1442.