Should intervening rights apply to claims that were not textually amended during a reexamination proceeding but were effectively narrowed by the patentee’s arguments? Following a controversial panel decision last September in Marine Polymer Technologies, Inc. v. Hemcon, Inc. that expanded intervening rights for reexamination, an en banc Federal Circuit on March 15 ruled that intervening rights only apply if claim language is substantively amended or new claims are added. In a closely divided 6-4 ruling, the court specifically rejected the original panel’s determination that intervening rights can arise as a result of the patentee’s statements to the U.S. Patent and Trademark Office (“PTO”) during reexamination that effectively limit the claim but do not result in an amendment to the claim language.

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