Restriction Requirements as Substantive Limiters: Lessons from Focus Products v. Kartri

Restriction requirements are often treated as administrative noise—something to get past on the way to allowance. The Federal 2025 decision in Focus Products Group International, LLC v. Kartri Sales Co. shows how dangerous that mindset can be. In that case, a species restriction and the patentee’s handling of it became the backbone of a prosecution history disclaimer argument that narrowed claim scope enough to wipe out two patent infringement wins.

I. From hookless curtains to “flat upper edge” rings

Focus Products arises from a dispute over “hookless” shower curtains with embedded rings. Focus asserted three related patents—the ’248, ’609, and ’088 patents—along with HOOKLESS‑related trademark and trade dress rights. After a bench trial, the Southern District of New York construed “ring” broadly as “a piece of material that is curved at least in part and that generally encloses and reinforces an opening,” rejected prosecution‑history‑based limits on ring shape, and found Marquis liable for infringing all three patents. Focus Prods. Grp. Int’l, LLC v. Kartri Sales Co., No. 1:15‑cv‑10154 (PAE), 2018 WL 3773986, at *4–6 (S.D.N.Y. Aug. 9, 2018).

On appeal, the Federal Circuit agreed that “ring” does not require any particular overall geometry. But it held that, in the ’248 and ’609 patents, the term cannot be read to cover rings with a “flat upper edge.” Focus Prods. Grp. Int’l, LLC v. Kartri Sales Co., Nos. 2023‑1446, ‑1450, ‑2148, ‑2149, slip op. at 16–22 (Fed. Cir. Sept. 30, 2025). Everyone agreed that Marquis’s accused rings have a flat upper edge, so once that limitation was excluded from the scope of “ring,” the infringement findings on the ’248 and ’609 patents could not stand. Id. at 15–16.

The way the panel reached that narrowing is the real story. The court did not find the limitation in the claim language itself or the specification alone. Instead, it relied on how the PTO initially split the invention into species in the ’248 prosecution, the patentee’s election of one species without traverse, the later addition and withdrawal of a dependent claim reciting a “flat upper edge,” and the patentee’s decision in prosecuting the ’088 patent to add an explicit “flat upper edge” limitation to overcome a nonstatutory double‑patenting rejection. Taken together, those steps “paint[ed] a clear and consistent picture” that rings with a flat upper edge were surrendered for the ’248 and ’609 patents and reserved instead for the later ’088 patent. Id. at 17–22.

II. The restriction requirement in the ’248 and ’609 prosecutions

The starting point is the original ’248 application. That application claimed multiple ring configurations, corresponding to several different figures. The examiner issued a species‑type restriction requirement, identifying patentably distinct ring species mapped to particular drawings. Species IV corresponded to Figures 18–20; Species V corresponded to Figure 21. Id. at 17–18.

Figures 18–20 depict rings with a projecting edge or “finger” extending from the ring, which helps support the curtain on the rod. Figure 21, by contrast, shows a ring with a relatively long, flat upper edge, providing support over a span roughly equal to the ring’s outer diameter. Id. at 17–18. The restriction requirement thus drew a structural line between “projecting finger” rings and “flat upper edge” rings.

The applicant elected Species IV and did not traverse or otherwise challenge the examiner’s definition of the species. Id. at 18. After the election, it added a number of new claims. One of them, dependent claim 73, recited that the “ring includes a flat upper edge along at least a portion of said ring.” Id. at 18–19. The examiner reacted by withdrawing claim 73 from consideration as drawn to a nonelected species—Species V tied to Figure 21—while allowing its base claim, directed to a ring with a projecting finger, to remain in the elected group. Id.

At that point, the record reflected a clear delineation: in the examiner’s view, a “ring” in the elected Species IV did not include a flat upper edge, and any claim explicitly reciting a flat upper edge was part of the nonelected Species V. The patentee did not object to that characterization. It continued prosecution on the remaining claims without traversing the restriction or arguing that flat‑upper‑edge embodiments were also within the elected invention. Id. at 19–20.

The Notice of Allowance made the issue even more explicit. The examiner reiterated that claim 73 remained withdrawn as nonelected subject matter and indicated that the applicant could challenge that outcome if it found the cancellation “unacceptable.” The patentee again did nothing to contest the exclusion of claim 73. Instead, it amended other claims and allowed the prosecution to proceed to allowance with claim 73 still cancelled as nonelected subject matter. Id. at 20.

The ’609 prosecution followed the same pattern. The examiner issued a similar restriction requirement, again distinguishing Species IV (Figures 18–20) from Species V (Figure 21), and the applicant again elected Species IV without traverse. The Federal Circuit treated the ’609 prosecution history as materially parallel to the ’248 history on this point. Id. at 19 n.7.

By the time both patents issued, the intrinsic record contained three key elements: a figure‑based restriction that expressly segregated flat‑upper‑edge rings into a different species; repeated withdrawal of a flat‑upper‑edge claim as nonelected subject matter; and the patentee’s consistent acquiescence in that framework.

III. The reinforcing role of the ’088 prosecution

The prosecution of the later‑filed ’088 patent completed the picture. Initially, the examiner rejected the ’088 claims for nonstatutory obviousness‑type double patenting over the ’248 and ’609 patents. Id. at 21. To overcome that rejection, the applicant amended the claims to add, among other features, a limitation requiring that the ring have “a flat upper edge.” Id.

The examiner then withdrew the double‑patenting rejection. In doing so, the examiner explained that the newly added “flat upper edge” limitation distinguished the ’088 patent from the earlier patents, because that feature was tied to a species not claimed in the ’248 and ’609 patents. Id. at 21–22. The patentee accepted that explanation and continued prosecution on that understanding.

Thus, across three related prosecutions, both the applicant and the PTO treated “flat upper edge” rings as belonging to a different species than the rings claimed in the ’248 and ’609 patents. In the Federal Circuit’s view, that history confirmed that the earlier patents did not cover flat‑upper‑edge rings, while the ’088 patent did.

IV. From restriction to disclaimer

Against this backdrop, the Federal Circuit turned to prosecution history disclaimer. Under settled law, claim terms are generally given their full ordinary meaning unless the patentee clearly and unmistakably disavows certain scope during prosecution. Thorner v. Sony Comput. Ent. Am. LLC, 669 F.3d 1362, 1365 (Fed. Cir. 2012). Courts are reluctant to narrow claims based solely on ambiguous exchanges with the PTO or on unilateral examiner characterizations that the applicant does not clearly adopt. See, e.g., Innova/Pure Water, Inc. v. Safari Water Filtration Sys., Inc., 381 F.3d 1111, 1124 (Fed. Cir. 2004); Biogen Idec, Inc. v. GlaxoSmithKline LLC, 713 F.3d 1090, 1097 n.6 (Fed. Cir. 2013).

The patentee relied heavily on Plantronics, Inc. v. Aliph, Inc., where the Federal Circuit held that an election in response to an ambiguous restriction requirement could not, by itself, support a disclaimer of claim scope. 724 F.3d 1343, 1350–51 (Fed. Cir. 2013). In Plantronics, neither the examiner nor the applicant said anything specific about what structurally distinguished the elected and nonelected species, so the court declined to treat the election as a clear surrender of subject matter. Id. at 1351.

The Focus Products panel distinguished that scenario. It acknowledged that an election made in response to a vague restriction requirement cannot, on its own, narrow a claim. Focus Prods., slip op. at 16. But it emphasized that this case involved more than a one‑off election: the restriction mapped to specific figures with distinct structures; the examiner repeatedly enforced that boundary by withdrawing the only claim explicitly reciting a flat upper edge as nonelected subject matter; the patentee repeatedly acquiesced, even when invited to contest that treatment; and in a later case, the patentee affirmatively used “a flat upper edge” to distinguish the ’088 claims over the ’248 and ’609 patents in a double‑patenting context. Id. at 17–22.

On that record, the court concluded that the applicant had clearly accepted an understanding of the ’248 and ’609 patents under which “ring” did not encompass flat‑upper‑edge rings. The term therefore could not be construed at trial to cover such rings, even though the claim language itself, read in isolation, did not expressly exclude them. Id. at 22. Because the accused products all had a flat upper edge, the Federal Circuit reversed the infringement judgment on the ’248 and ’609 patents. Id. at 15–16, 22.

V. Doctrinal significance

Doctrinally, Focus Products illustrates how restriction practice can contribute to a robust disclaimer record when combined with later prosecution choices. It does not abandon Plantronics’ caution about treating elections as substantive surrenders, but it makes clear that an election is not hermetically sealed from the rest of the file history. When the examiner defines species by specific drawings that reflect distinct structural concepts, when that line is repeatedly enforced through cancellation of nonelected claims, and when the applicant later leans on the same structural feature to carve around earlier family members, a court may find the “clear and unmistakable” evidence required for disclaimer.

The decision also refines the treatment of examiner statements. Cases like Biogen warn that silent acquiescence in an examiner’s Reasons for Allowance should not usually be treated as a surrender of claim scope. 713 F.3d at 1097 n.6. In Focus Products, the Federal Circuit characterized the patentee’s conduct as more active than mere silence: the applicant elected a species, accepted the examiner’s repeated characterization of flat‑upper‑edge claims as nonelected subject matter, declined an explicit invitation to challenge that characterization in the Notice of Allowance, and then capitalized on the same distinction to overcome a double‑patenting rejection in a related case. Focus Prods., slip op. at 20–22. That pattern gave the examiner’s understanding of the species boundary more weight than a one‑off unilateral statement.

VI. Practical implications for prosecution and litigation

For prosecutors, Focus Products is a reminder that restriction practice can have long‑term consequences, especially when the line between species tracks commercially important features. When a restriction requirement expressly separates embodiments by a structural limitation—such as “flat upper edge” versus “projecting finger”—counsel should think carefully before treating the election as a mere formality. Options can include traversing the restriction, clarifying on the record that the elected claims are not limited to the examiner’s characterization, or preserving the ability to pursue nonelected subject matter in a divisional and making that intent explicit.

Allowing a dependent claim that recites the key feature to be withdrawn as nonelected subject matter, and then ignoring a Notice of Allowance that reiterates that withdrawal and invites challenge, risks creating exactly the kind of record the Federal Circuit relied on here. Once that record exists, later arguments that the claim term should be read broadly enough to reach the nonelected feature may face an uphill battle.

Related‑application strategy also matters. In Focus Products, amending the ’088 claims to add a “flat upper edge” limitation and relying on that limitation to overcome a double‑patenting rejection provided powerful confirmation that the earlier patents did not cover that feature. Prosecutors should assume that anything said in one family member about how it differs from another will be used to interpret both.

For litigators, the decision underscores the importance of digging deeply into restriction requirements and family‑wide prosecution history. The sequence of restriction, election, cancelled claims, and later amendments that carried the day in Focus Products is not uncommon in complex portfolios. Accused infringers should treat restriction practice as a fertile source of narrowing arguments; patentees should review those records early to identify potential vulnerabilities and develop realistic constructions.

VII. Conclusion

In Focus Products v. Kartri, the Federal Circuit turned what might have looked like routine restriction practice into a decisive claim‑construction tool. By tying the scope of “ring” in the ’248 and ’609 patents to a species restriction that separated flat‑upper‑edge rings from projecting‑finger rings, the patentee’s election without traverse, the withdrawal and abandonment of a flat‑upper‑edge dependent claim, and a later amendment in the ’088 prosecution that used “flat upper edge” to distinguish over the earlier patents, the court found a clear and unmistakable disclaimer of flat‑upper‑edge rings.

The larger lesson is straightforward. Restriction requirements are not always mere docket‑management devices. When they draw lines around meaningful features and the applicant cooperates with those lines over time, they can narrow claim scope in ways that matter years later. Treating them as harmless housekeeping, rather than as part of the substantive record, is a luxury modern patent practice may no longer afford.