Marking is the act of placing a patent number on a product or its packaging. The doctrine of marking estoppel deals with whether the act of marking will preclude denials of patent infringement or patent validity challenges. This comment reviews the history of marking estoppel and determines that although the Federal Circuit has expressed reservations about the doctrine, marking estoppel remains viable. This comment argues that marking estoppel should preclude a marking party from denying patent infringement when the marking party has acted with scienter and the asserting party has come to court with clean hands. However, because of the important public interest in having only valid patents in the marketplace, marking estoppel should not preclude patent validity challenges. In light of the Supreme Court’s decision in MedImmune, marking estoppel could become a powerful shield for increasingly defenseless patentees.
Michael D. Karson, Rediscovering the Doctrine of Marking Estoppel After Medimmune: Balancing the Public Interest and Private Rights, 7 J. Marshall Rev. Intell. Prop. L. 573 (2008)