The Patent Reform Act of 2005 modifies the existing “inter partes reexamination” proceeding established in The American Inventors Protection Act of 1999. Inter partes examination proceedings differ from the proposed post-grant opposition proceedings in that inter partes reexaminations are available at any time during the life of the patent and are limited to patentability issues based on earlier patents or publications describing the invention at issue.

The Committee proposal expands inter partes reexaminations by removing the limitation that a requester is estopped from asserting at a later time patent invalidity on any ground that the requester “could have raised” during the reexamination proceeding. Of course, the original limitation was intended to balance the equities involved in inter partes reexamination, and comported with fundamental notions of fairness. This is no different than what occurs if an infringer is sued in court and, having argued invalidity and losing, that same infringer cannot later bring a second lawsuit seeking to invalidate the same patent.