Federal Circuit Invalidates Patents Over Missing Coinventor——Fortress Iron Decision Reinforces Strict Inventor Requirements

On April 2, 2026, the U.S. Court of Appeals for the Federal Circuit affirmed the invalidation of two U.S. patents (Patent Nos. 9,790,707 and 10,883,290) owned by Fortress Iron LP in a decision that underscores the strict requirements for proper inventor designation under U.S. patent law. The decision, written by Judge Lourie, found that the patents were invalid because the patent applications failed to list all coinventors who had substantially contributed to the conception of the invention.

The case involved a vertical cable rail barrier technology developed through collaboration between two Fortress Iron employees and two employees of Quan Zhou Yoddex Building Material Co., Ltd., a Chinese building materials company. Despite the joint conception and development effort, the issued patents listed only the Fortress Iron inventors. The two Chinese employees who had substantively contributed to the design were omitted from the patent documents.

Following the district court’s grant of summary judgment invalidating both patents, the Federal Circuit affirmed on appeal. This decision reaffirms a critical principle in U.S. patent law: the omission of a coinventor constitutes a fundamental defect that destroys patent validity independent of substantive patentability issues under 35 U.S.C. sections 101 or 103. A patent cannot stand if it fails to properly identify all persons who contributed to the inventive concept.

The practical implications for patent practitioners and international R&D teams are significant. When inventions result from multinational collaboration, every individual who substantially conceived of or reduced to practice a limitation claimed in the patent must be identified and listed as an inventor. Failure to do so exposes the patent to complete invalidation, regardless of the technical merit of the underlying innovation.

Under U.S. patent law, an inventor is defined as any person who contributes to the conception of a claimed invention. The determination of inventorship requires careful factual analysis in each case. The Fortress Iron decision serves as a cautionary reminder that proper inventor designation is not merely administrative formality——it is a foundational requirement for patent validity. For organizations engaging in cross-border development projects, meticulous attention to inventor identification during the patent filing process is essential.