Inter Partes Review Estoppel: Restoring The Principles Of Res Judicata

46 Pages Posted: 4 Mar 2020 Last revised: 6 Apr 2020

Date Written: February 3, 2020


Inter partes review estoppel has violated the principles of traditional res judicata since its inception. For the first several years of its life, IPR estoppel served to preserve a petitioner’s ability to harass patent owners and repetitively attempt to invalidate patents. Following SAS in 2018, IPR estoppel began to reverse course. The courts that once were allowing patent owner abuse are now limiting it with a broad application of IPR estoppel. However, this broad application of IPR estoppel is a soft claim preclusion that allows many exceptions behind the principles of res judicata. Furthermore, the PTAB allows petitioners to file numerous IPR petitions and does not enforce estoppel until a final written decision is issued to which the petitioner is a real party in interest. This practice likewise allows the harassment of patent owners and violates the principles of res judicata.

To resolve the inter partes review estoppel problems, Congress must reintroduce the principles of res judicata with exceptions only where patent litigation absolutely requires it. Such an analysis leads to the conclusion that by enacting only the petitioner standing requirement and the estoppel provisions of the STRONGER Patents Act of 2019, IPR estoppel would achieve a balance equitable to patent owners and petitioners alike. These two provisions do well to support the principles of res judicata, grant adequate leeway where patent litigation requires it, yet still provide claim preclusion strong enough to avoid abuse. The doctrine of res judicata does not need reinventing for 21st century patent litigation—it merely needs reintegration.

Keywords: inter partes review, ipr, estoppel, res judicata, Stronger Patents Act

Suggested Citation

Modderman, Matthew, Inter Partes Review Estoppel: Restoring The Principles Of Res Judicata (February 3, 2020). Available at SSRN: or

Matthew Modderman (Contact Author)

University of Akron School of Law ( email )

Akron, OH
United States

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