Inter partes reviews: the effect of estoppel

The inter partes review (IPR) process is now three years old, and the effects on subsequent proceedings are beginning to be seen. Under the 2011 America Invents Act (AIA), IPR petitioners are estopped from asserting invalidity in a civil action or International Trade Commission investigation on any ground that the petitioner “raised or reasonably could have raised” in a previous IPR that resulted in a final written decision.