IP Law Daily, PATENT—Fed. Cir.: Invalidity of railing system patents affirmed in dispute between competing building products companies, (Apr 6, 2026)

By Ravindra Kumar Singh, B.L.

The appellate court ruled that the district court correctly found the patents invalid because an undisputed co-inventor was omitted and could not be added under statutory requirements.

The U.S. Court of Appeals for the Federal Circuit affirmed a federal district court’s summary judgment ruling that two patents relating to railing systems were invalid due to incorrect inventorship, concluding that the omission of a coinventor could not be cured under 35 U.S.C. § 256. The appellate court further upheld the denial of the patentee’s request to correct inventorship, finding that statutory requirements, including notice to all parties concerned, were not satisfied (Fortress Iron, LP v. Digger Specialties, Inc., No. 24-2313 (Fed. Cir. Apr. 2, 2026)).

Background. Fortress Iron, LP, the plaintiff-appellant, designs and sells railing and fencing systems used in outdoor construction projects. Digger Specialties, Inc., the defendant-appellee, manufactures competing building and construction products, including railing systems. The asserted U.S. Patent Nos. 9,790,707 (the ’707 patent) and 10,883,290 (the ’290 patent) relate to pre-assembled vertical cable railing panels designed to simplify installation. The inventions addressed technical issues associated with cable rotation during tensioning by incorporating specific design modifications developed during collaboration with manufacturing partners.

Fortress Iron filed this lawsuit in the Northern District of Indiana in January 2021, alleging infringement of the ’707 and ’290 patents. During discovery, Digger Specialties identified two additional contributors to the invention who had not been named as inventors. Fortress Iron later acknowledged that both individuals were coinventors. It successfully added one of them through administrative procedures but was unable to locate the other. Fortress Iron then moved for partial summary judgment seeking correction of inventorship under 35 U.S.C. § 256(b), while Digger Specialties moved for summary judgment of invalidity. The district court denied Fortress Iron’s motion and granted Digger Specialties’ motion, holding that the patents were invalid due to the omission of a coinventor. Fortress Iron appealed.

Inventorship requirement. The Federal Circuit reaffirmed that correct inventorship is a fundamental requirement of patent validity. Citing Pannu v. Iolab Corp., 155 F.3d 1344 (Fed. Cir. 1998), the court noted that the nonjoinder of a true inventor renders a patent invalid. While 35 U.S.C. § 256 provides a mechanism to correct such errors, the court emphasized that the statute operates as a “savings provision” only where its requirements are satisfied.

“Party concerned” requirement. The central issue on appeal was whether the omitted coinventor qualified as a “party concerned” under § 256(b), thereby requiring notice and an opportunity to be heard before correction could be ordered. The Federal Circuit agreed with the district court that he did. Relying on Chou v. University of Chicago, 254 F.3d 1347 (Fed. Cir. 2001), the court held that inventors are inherently “parties concerned,” regardless of whether they currently hold ownership interests.

Because Fortress Iron was unable to locate the omitted co-inventor, it could not provide the statutory notice or opportunity for a hearing. The court stressed that these procedural safeguards are mandatory prerequisites, not discretionary considerations. As a result, Fortress Iron could not invoke § 256(b) to correct inventorship.

Statutory interpretation rejected. The Federal Circuit rejected Fortress Iron’s argument that “party concerned” should be limited to individuals with an economic interest in the patent. Such an interpretation, the court explained, would improperly rewrite the statute. Citing Newport News Shipbuilding & Dry Dock Co. v. Garrett, 6 F.3d 1547 (Fed. Cir. 1993), the court reiterated that it could not alter statutory language.

The court also rejected the appellant’s attempt to equate “party concerned” with constitutional standing, noting that the two concepts are distinct. Even in the absence of present ownership rights, inventors retain significant legal and financial interests in a patent, including potential co-ownership rights under 35 U.S.C. § 262, as recognized in Ethicon, Inc. v. U.S. Surgical Corp., 135 F.3d 1456 (Fed. Cir. 1998).

Invalidity for omitted inventor. Turning to invalidity, the court held that the district court correctly concluded that the patents were invalid because the inventorship error could not be corrected. Interpreting § 256(b), the court explained that while the statute preserves validity where errors “can be corrected,” the opposite implication applies where correction is not possible.

Fortress Iron argued that naming at least one true inventor should suffice for validity. The Federal Circuit rejected this position, explaining that the statutory framework, including 35 U.S.C. §§ 100(f) and 101, requires that all inventors be named where an invention is jointly made. To hold otherwise would render § 256’s corrective mechanism superfluous. Citing Sharp v. United States, 580 F.3d 1234 (Fed. Cir. 2009), the court emphasized that statutory provisions must be interpreted to give effect to every clause. It further noted longstanding precedent establishing that nonjoinder of an inventor invalidates a patent, reinforcing the continued vitality of this principle even after the repeal of 35 U.S.C. § 102(f).

Thus, the appellate court affirmed the district court’s denial of Fortress Iron’s request for correction under § 256(b) and its grant of summary judgment of invalidity in favor of Digger Specialties.

The Case is No. 24-2313.

Judge: Lourie, A.

Attorneys: Paul V. Storm (Foley & Lardner LLP) for Fortress Iron, LP. Heather B. Repicky (Barnes & Thornburg LLP) for Digger Specialties, Inc.

Companies: Fortress Iron, LP; Digger Specialties, Inc.

Cases: Patent FedCirNews