Legal Estoppel

  • Legal Estoppel Is Ancillary To Rights Conveyed To Related Patent: “Legal estoppel refers to a narrow[] category of conduct encompassing scenarios where a patentee has licensed or assigned a right, received consideration, and then sought to derogate from the right granted.” Transcore (Fed. Cir. 04/08/09) (legal estoppel blocks assertion of later-issued broader patent to extent abrogates rights granted by covenant not to sue under earlier patent.) “A license or a covenant not to sue enumerating specific patents may legally estop the patentee from asserting continuations of the licensed patents in the absence of mutual intent to the contrary.” Endo Pharm. (Fed. Cir. 03/31/14) (2-1) (taking narrow view of Transcore; legal estoppel does not extend to patents asserting priority to same provisional appln. as licensed patent, but not continuations of licensed patent, where license disavowed implied licenses); Cheetah Omni (Fed. Cir. 02/06/20) (aff’g Summ. J., license of patent impliedly licensed continuation of continuation thereof, under doctrine of legal estoppel, whether or not claims are broader or narrower); General Protecht (Fed. Cir. 07/08/11) (applying Transcore: a covenant not to sue that certain products infringe certain patents impliedly licenses later continuation patents, even if they have narrower claims, as to those particular products, absent a clear indication of mutual intent to the contrary). See Wang Labs (Fed. Cir. 01/03/97) (distinguishing legal estoppel and equitable estoppel).

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