Can the scope of patent claims be enlarged during reexamination?

No, the scope of patent claims cannot be enlarged during reexamination. This limitation is explicitly stated in 37 CFR 1.530(j):

“No amendment may enlarge the scope of the claims of the patent or introduce new matter. No amendment may be proposed for entry in an expired patent. Moreover, no amendment, other than the cancellation of claims, will be incorporated into the patent by a certificate issued after the expiration of the patent.”

This rule ensures that reexamination proceedings do not extend patent rights beyond what was originally granted or introduce new subject matter not supported by the original disclosure.

All Amendments Must Be Fully Presented MPEP 2234 Required
Amendments Required for Merged Reexamination Proceedings MPEP 2234 Informative
Amendments Must Comply With Specific Requirements for Reexamination MPEP 2234 Required
Claims Must Follow Highest Numbered Claim During Reexamination MPEP 2234 Prohibited
Claims and Descriptions Must Be Fully Presented For Any Amendment MPEP 2234 Required