On May 7, 2025, the United States Court of Appeals for the Federal Circuit issued a pivotal decision in Ingenico Inc. v. IOENGINE, LLC that significantly narrows the scope of inter partes review (IPR) estoppel under 35 U.S.C. §315(e)(2). The court clarified that IPR estoppel does not apply to invalidity arguments based on product prior art, such as public use or on-sale activities, and is instead limited to patents and printed publications. This decision represents a landmark interpretation of estoppel provisions under the America Invents Act (AIA) and has wide-reaching implications for patent litigation strategy in 2025 and beyond.

What Is IPR Estoppel Under §315(e)(2)?

Under 35 U.S.C. §315(e)(2), a party that has instituted an IPR and receives a final written decision is estopped from later asserting in district court “that the claim is invalid on any ground that the petitioner raised or reasonably could have raised during that inter partes review.” Traditionally, courts have broadly interpreted this language to mean that once an IPR concludes, the petitioner cannot later raise any prior art grounds that were reasonably available—whether or not they were actually used. However, the Ingenico ruling draws a sharper line, focusing only on what kinds of prior art estoppel applies to.

Case Background: Ingenico v. IOENGINE

Parties:

• Plaintiff: IOENGINE, LLC

• Defendant: Ingenico Inc., a leading provider of payment terminals

Litigation Timeline:

• IOENGINE sued Ingenico for patent infringement.

• Ingenico filed an IPR petition against IOENGINE’s asserted patents.

• The PTAB issued a final written decision.

• IOENGINE argued that Ingenico should be estopped from raising any invalidity grounds in district court—including product prior art.

   

Central Question: Does IPR estoppel apply to non-documentary prior art, such as physical products or systems in public use or on sale before the patent’s critical date?

The Federal Circuit’s Holding

The court ruled in favor of Ingenico, holding that §315(e)(2) estoppel does not bar invalidity arguments based on product prior art, including:

• Devices publicly used

• Systems offered for sale

• Demonstrations at trade shows

The ruling emphasized the statutory text: IPR proceedings are limited to grounds “based on patents or printed publications.” Thus, if a ground could not be raised in an IPR—because it involved physical products or public use—then it cannot trigger estoppel.

“Congress deliberately restricted the scope of IPR to documentary evidence—printed publications and patents. To extend estoppel to include non-documentary prior art would stretch the statute beyond its plain meaning.” – Excerpt from the opinion

Implications for Patent Litigation Strategy in 2025

1. Renewed Importance of Product Prior Art

Patent defendants now have stronger incentives to hold back product-based prior art for district court litigation. This allows them to hedge their invalidity defenses—arguing certain grounds in IPR and saving others for trial.

For a broader understanding of how physical evidence fits into invalidity arguments, read our guide on Patent Invalidation Searches: Protecting Against Infringement Claims.

2. Tactical Dual-Path Defense

Expect a rise in hybrid invalidity strategies, where defendants pursue IPRs on documentary prior art while reserving:

• Device manuals

• Public use demonstrations

• Legacy system deployments

Learn more about how to segment different types of prior art effectively in our blog on FTO Search vs. Patentability Search.

3. Limits of IPR as a One-Stop Shop

This ruling weakens the perception of IPR as a full substitute for litigation. IPRs now handle only a subset of possible invalidity grounds. Petitioners must carefully weigh what to include and what to save.

4. Shift in Settlement Leverage

Plaintiffs can no longer assume all invalidity arguments are estopped post-IPR. This affects settlement dynamics, as defendants may retain credible invalidity positions even after losing at the PTAB.

Legal Commentary & Expert Reactions

According to Winston & Strawn LLP, the decision aligns with their long-held position that estoppel should not penalize parties for failing to raise grounds they legally could not bring before the PTAB.

Gemini Law Group noted that this ruling could re-balance power in tech-heavy patent cases, where product-based prior art (like embedded systems) is often crucial but undocumented.

Patent litigation experts also suggest that the Federal Circuit may have intentionally narrowed estoppel to preserve due process and avoid penalizing defendants for procedural limitations of the IPR framework.

For a real-world example of patent enforcement outcomes, see our breakdown of Patent Enforcement in Action: Lessons from Nokia vs. Amazon.

Historical Context: Estoppel Evolution Post-AIA

• 2018 – California Institute of Technology v. Broadcom: Broad estoppel applied to all grounds reasonably available, including those not raised.

• 2020–2023 – District courts split: Some applied broad estoppel to nearly all invalidity defenses.

• 2025 – Ingenico v. IOENGINE: Definitive limitation: estoppel is constrained to printed publications and patents only.

This evolution underscores a long-running tension between efficiency and fairness in post-grant proceedings.

To ensure your invalidity arguments are comprehensive, also read our primer on Understanding Patent Prior Art Search.

FAQs: IPR Estoppel After Ingenico v. IOENGINE

Q1. Does IPR estoppel now apply only to patents and printed publications?
Yes. The Federal Circuit’s 2025 ruling explicitly states that estoppel under §315(e)(2) is limited to invalidity grounds that are based on printed publications and patents.

Q2. Can defendants still raise product prior art in district court?
Absolutely. If the prior art involves a physical product, public use, or a system offered for sale, it can be raised post-IPR.

Q3. How should companies prepare their invalidity strategy now?
Defendants should segment their prior art early—submit publications to IPR and reserve physical/system-based art for court.

Q4. Will this ruling increase the cost of litigation?
Potentially, yes. With more invalidity grounds surviving into trial, litigation could become more complex and expensive.

Conclusion: A New Chapter for IPR and Litigation Strategy

The Ingenico v. IOENGINE decision redefines the reach of IPR estoppel, restoring a vital lane for product-based prior art in litigation. Patent practitioners in 2025 must realign their invalidity strategies to reflect this narrower interpretation of §315(e)(2).

As we move forward, defendants will likely embrace a dual-track approach, maximizing the IPR process while preserving critical non-documentary art for court.

This case is a must-watch for patent litigators, in-house counsel, and innovators alike.

Need help aligning your IP strategy post-Ingenico?
Contact our patent litigation specialists for a free consultation.