Wednesday, March 10, 2021
The assignor estoppel doctrine (“AED”) is an equitable doctrine based on the principle of fair dealing that prevents assignors of patent rights, and those in privity with them, from challenging the validity of the assigned rights under many circumstances. The classic fact pattern in which the AED is invoked involves an inventor/assignor assigning his or her patent rights for value and then seeking to invalidate such patent rights when sued for infringement of the assigned rights.
The Supreme Court has recognized this doctrine on a number of occasions, but each time, it has done so sparingly and has tightly constricted it.