In Minerva Surgical v. Hologic, the U.S. Supreme Court limited the scope of the patent law concept of assignor estoppel in several key respects. Despite those limitations, assignor estoppel may remain important in certain industries, such as life and physical science start-up companies that develop and commercialize the work of academic-inventors.

Assignor estoppel is a judge-made “equitable doctrine that prevents one who has assigned the rights to a patent (or patent application) from later contending that what was assigned is a nullity.” Hologic v. Minerva Surgical, 957 F.3d 1256, 1264 (Fed. Cir. 2020). In other words, the doctrine promotes fairness by preventing those who assign patent rights from later claiming that what was assigned is valueless. The doctrine relies on the notion that it would be “an injustice” to “allow the assignor to make that representation [of validity] at the time of the assignment (to his advantage) and later to repudiate it (again to his advantage).” Minerva, 141 S. Ct. at 2304 (quoting Hologic, 957 F.3d at 1265).