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This Comment seeks to resolve a dispute among district courts on how to interpret the term “ground” in 35 U.S.C. § 315(e)(2), the America Invents Act’s (AIA) estoppel provision. The question of whether a party that asserts a printed publication or patent in an inter partes review (IPR) proceeding is estopped from asserting real- world prior art, such as a device, in a later civil action under § 315(e)(2) has resulted in a district court split. Some courts have construed the estoppel provision narrowly, reasoning that because a physical object like a device is not something that could have been raised during IPR, estoppel cannot apply. Under this interpretation, “ground” is interpreted to mean a piece of evidence. Because physical products are not the same type of evidence offered during IPR, litigants are not estopped from using them in later civil actions. On the other side of this, courts have determined that estoppel can apply, but does not in situations where the physical object being raised is either “superior and separate” or presents a “substantive difference” to the paper prior art raised in IPR. Here, “ground” is interpreted to mean argument, such that estoppel applies when the device offers no arguments other than those already put forth during IPR—in other words, when litigation would be duplicative. The resolution to this question carries significant consequences for the cost, efficiency, and institutional division of labor of the patent system.

This Comment argues that the AIA’s text and purpose support adopting the substantive difference approach. This approach strikes a workable balance in focusing on the legal arguments to ensure that litigants are not unduly relitigating the same arguments already decided by the Patent Trial and Appeal Board (PTAB). The substantive difference approach also advances the AIA’s purpose in offering IPR as a cheaper, faster alternative to district court litigation. It also promotes a reasonable division of responsibilities between the PTAB and district courts. Overall, as this Comment explains, this interpretation best aligns with the patent system’s goals

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