Federal Circuit Affirms Patent Invalidity Where Inventorship Error Cannot Be Corrected Under 35 U.S.C. §256

On April 2, 2026, the U.S. Court of Appeals for the Federal Circuit affirmed summary judgment invalidating two patents based on improper inventorship. The decision arose from Fortress Iron, LP v. Digger Specialties, Inc., No. 2024-2313 (Fed. Cir. Apr. 2, 2026). In a case of first impression, the Court addressed whether an omitted coinventor is a “party concerned” under §?256(b). The Court held that omission of an undisputed joint inventor rendered the patents invalid where correction under the statute was not possible.

The patents involved, U.S. Patent Nos. 9,790,707 (“the ‘707 patent”) and 10,883,290 (“the ‘290 patent”), each assigned to Fortress Iron, LP (“Fortress”), are directed to pre-assembled vertical cable railing panels. Fortress developed the products through a collaborative process involving internal personnel as well as overseas manufacturing and quality-control partners. After Fortress’s initial concept and design work, employees of a third-party partner proposed specific design changes to address cable tensioning problems discovered during prototyping. Those changes were incorporated into the final product, and the two individuals who proposed the changes were subsequently acknowledged to be joint inventors of the patented subject matter. When Fortress initially filed the two patent applications covering the final product, however, only its internal personnel were named as inventors.

After the ‘707 and ‘290 patents issued, Fortress asserted them against Digger Specialties, Inc. for infringement. During the course of the litigation, it was determined—and ultimately undisputed—that those two individuals from the third-party partner qualified as joint inventors (Fortress Iron, LP v. Digger Specialties, Inc., 748 F. Supp. 3d 614, 618–19 (N.D. Ind. 2024)). Fortress sought to correct inventorship and successfully added one omitted coinventor to the patents following the procedure outlined in §?256(a). However, the second omitted coinventor could not be located or contacted, and Fortress conceded that it could not add him using the same procedure. Because Fortress could not provide notice to that inventor, the district court denied correction of inventorship under §?256(b) and granted summary judgment that the patents were invalid for omission of an inventor, prompting Fortress to appeal to the Federal Circuit.

Section?256 of the Patent Act provides a limited “savings provision,” allowing inventorship errors to be corrected without invalidating a patent, but only if the statute’s procedural requirements are met. In particular, §?256(b) authorizes a court to order correction of inventorship “on notice and hearing of all parties concerned.” Fortress relied on that provision, arguing in its appeal to the Federal Circuit that the omitted coinventor was not a “party concerned” because correction would not adversely affect ownership or economic interests in the patents. Fortress also argued that the district court erred by construing §?256 too narrowly, asserting that courts are to apply the provision broadly and permissively due to its “savings provision” status.

The Federal Circuit rejected those arguments. Relying on Chou v. University of Chicago, 254 F.3d 1347 (Fed. Cir. 2001), the Court held that an omitted coinventor is a “party concerned” under §?256(b) and is therefore entitled to notice and an opportunity to be heard, based on inventorship status itself, regardless of assignment or whether correction would ultimately benefit or harm that individual. The Court declined to read “party concerned” through a due process or economic interest lens, emphasizing instead that inventors occupy a central role in the patent system and that inventorship may carry legal, financial, and ownership consequences. The statute’s notice and hearing requirement, the Court explained, is a mandatory prerequisite to relief.

Because Fortress could not provide notice to one of the omitted coinventors, the inventorship error could not be corrected under §?256. The Federal Circuit further explained that §?256 operates as a “savings provision” only when correction is possible. Where, as here, the omission of a true inventor cannot be remedied, the necessary implication of the statute is that the patent is invalid. The Court therefore affirmed summary judgment of invalidity.

The decision highlights the risk posed by delayed or informal inventorship determinations, particularly in collaborative development environments involving suppliers, contractors, or overseas partners. Notably, the outcome turned on Fortress’s inability to satisfy the statutory notice requirement rather than any dispute over the omitted individual’s status as a joint inventor. Even though the parties agreed on who the inventors were, the failure to satisfy the notice requirements of §?256 proved fatal.

Patent applicants should identify potential inventors early, carefully evaluate external technical contributions, and address inventorship questions as product designs evolve. As a practical matter, applicants may also wish to maintain reliable contact information for potential inventors, particularly where development involves outside contributors.