Background
When a company uses inter partes review (IPR) to challenge a patent before the Patent Trial and Appeal Board, federal law creates an “estoppel”: the petitioner cannot later assert in court that the challenged claims are invalid on “any ground that the petitioner raised or reasonably could have raised during that inter partes review.” (35 U.S.C. § 315(e)(2).) The practical question that divided district courts for years: what counts as a ground that “could have been raised” in an IPR?
IOENGINE, LLC held several patents covering portable USB-style communication devices and sued PayPal for infringement. Ingenico, a supplier of the accused payment terminals, filed IPR petitions and succeeded in having many claims invalidated. Several claims survived, however, and the case returned to district court for trial on those surviving claims. Ingenico then argued that earlier commercial products — physical devices, not patents or publications — had anticipated or rendered obvious the surviving claims.
IOENGINE countered that estoppel barred Ingenico from making those product-based arguments. The district court agreed with IOENGINE and entered judgment accordingly. Ingenico appealed to the Federal Circuit.
The Court’s Holding
The Federal Circuit reversed on the estoppel question, holding that § 315(e)(2) estoppel applies only to invalidity grounds based on patents or printed publications — the only categories of prior art that can be raised in an IPR. Grounds based on physical prior-art systems or products, public use, prior sales, or other non-printed prior art fall outside IPR estoppel entirely.
The court drew a careful distinction between a “ground” of invalidity and the evidence used to prove it. Estoppel is claim-specific and applies to legal theories, not individual pieces of evidence. Because IPR proceedings cannot consider physical prior-art products — only patents and printed publications — a system-art invalidity ground could never have been “raised” in the IPR, so it cannot be estopped.
The Federal Circuit also noted that the same physical prior art product could be described in a patent or printed publication, and that separately raising the description in an IPR would not estop reliance on the actual physical system in district court. The key is the legal ground — the statutory basis for invalidity — not the specific item of evidence.
The court denied rehearing en banc, leaving the ruling as final Federal Circuit law on the question.
Key Takeaways
- IPR estoppel is narrower than many assumed. Challengers who lose at the PTAB are only barred from re-asserting invalidity on grounds based on patents and printed publications — not on physical prior art or other non-printed bases.
- System art remains available post-IPR. After an IPR, petitioners may still argue in district court that a patent is invalid because prior-art physical products (devices, systems, machines) anticipated or rendered obvious the claims — even if those same products were referenced in publications used during the IPR.
- Prior-use and on-sale bars survive estoppel. Invalidity under § 102(a)(1)’s public use and on-sale bars — which cannot be raised in IPR — are not estopped, giving defendants a preserved path to invalidity arguments after an IPR concludes.
- Resolves a decade-long district court split. Before this decision, courts divided sharply on whether product art triggered estoppel. Patent defendants and their counsel can now plan IPR strategies with a clearer picture of what district-court arguments survive.
Why It Matters
The IPR estoppel question has been one of the most strategically important issues in patent litigation for years. Defendants filing IPRs often worried that a failed IPR could inadvertently wipe out their strongest invalidity arguments in court. Ingenico substantially alleviates that concern — at least for invalidity theories based on physical products rather than documents.
For patent defendants, the practical upshot is that going to the PTAB is now less of a gamble. An unsuccessful IPR does not foreclose arguing in court that physical prior art anticipated or obviated the claims. For patent owners, the ruling signals that winning an IPR on prior-art publication grounds does not guarantee freedom from a district-court invalidity challenge based on real-world products. Litigation strategy will need to account for both fronts.