After the fifth year of issuance of a U.S. trademark registration, the registration is eligible for “incontestable” status if the owner files a declaration with the U.S. Trademark Office confirming that (1) the mark has been in continuous use in U.S. commerce for the preceding five years and (2) there have been no adverse decisions regarding the ownership of the mark or the owner’s right to register it and no such proceedings are pending in a U.S. court or at the U.S. Trademark Office.

While “incontestable” status is of course desirable, there are many exceptions that allow challenges to be made against such a registration, such as fraud on the Trademark Office, abandonment/genericide of the mark, and functionality of the mark.  However, one of the open questions is whether an “incontestable” registration can be challenged by a prior user of the mark.  While many trademark owners would prefer certainty of ownership of “incontestable” registrations, some courts continue to leave open the possibility of challenge by a prior user.

One such case is the recent decision by the Southern District of California in Profil Institut fur Stoffwechselforschung GmbH v. ProSciento, Inc., 122 USPQ2d 1407 (S.D. Cal. 2017).  The court denied a motion to dismiss a claim to cancel an “incontestable” registration based on alleged prior use of the mark, acknowledging that “there is some inconsistency in decisional law” but ruling that 9th Circuit precedent allowed such a claim to proceed.  This case stands as a stark reminder to trademark owners that the “in” in “incontestable” can be misleading and that no one can guarantee that even an “incontestable” trademark registration is forever immune from attack.