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Examining the Recognition of Patent Infringement Warning Letters Based on Recent Judicial Decisions
Regarding the recognition of patent infringement warning letters, the Civil Judgment (113) Min-Gong-Su-Tzu No. 7, recently issued by the Intellectual Property and Commercial Court (hereinafter the "IP Court") clarified the scope of application concerning whether the issuance of specific letters falls under the Principles of the Fair Trade Commission in Handling Cases of Warning Letters Issued by Enterprise for Violation of Copyrights, Trademarks or Patents (hereinafter the "Principles"). Such judgment is worth noting.
In the current case, the Plaintiff is a manufacturer and distributor engaged in the production of wafers, power components, and control modules. Company A designs and manufactures chips and sells such chips to the Plaintiff. The Plaintiff then uses these chips to produce finished MOSFET assemblies, which are subsequently sold to Company B and Company C. Company B and Company C, in turn, commission contract manufacturers to assemble the MOSFET assemblies into end products, which are then distributed to various markets.
At the beginning of 2022, the Defendant discovered products on the market suspected of infringing its US patent. Following an investigation, the Defendant issued warning letters to the relevant companies within the same year, asserting several claims:
1. On May 23, 2022, the Defendant issued the First Warning Letter to Company A and Company B, alleging that the products of Company B infringed upon the Defendant’s U.S. Patent No. 409 (hereinafter referred to as the “Disputed U.S. Patent 409”).
2. On September 14, 2022, the Defendant issued the Second Warning Letter to Company B, Company B's U.S. subsidiary, and Company C. The Second Warning Letter claimed that certain product assemblies of Companies B and C (hereinafter referred to as the “Disputed Assemblies”) utilized the Defendant’s U.S. Patent No. 634 (hereinafter referred to as the “Disputed U.S. Patent 634”). The Defendant also enclosed a comparative illustrative analysis of the Disputed U.S. Patent 634 and the Disputed Assemblies, and recommended that the respective Companies notify the manufacturers and suppliers of the Disputed Assemblies.
3. On October 31, 2022, the Defendant issued the Third Warning Letter to Company B and its U.S. subsidiary, reiterating the explanations provided in the Second Warning Letter and inquiring once again about the progress of the case from Company B and its U.S. subsidiary.
The Plaintiff, as the manufacturer and seller of the Disputed Assemblies, asserted that the Defendant’s issuance of the aforementioned three Warning Letters failed to comply with the Principles. Specifically, the Defendant sent the Warning Letters directly to Company B, Company B's U.S. subsidiary, and Company C, none of which hold the status of manufacturer, importer, or agent, without first notifying the Plaintiff. The Plaintiff accordingly claimed that such conduct violated Articles 24 and 25 of the Fair Trade Act and caused damage to the Plaintiff. Consequently, the Plaintiff claimed for damages from the Defendant.
The IP Court dismissed the Plaintiff’s claims individually with the following reasons regarding each of the Warning Letters:
1. The First Warning Letter: The IP Court pointed out that the Defendant identified the allegedly infringing product as the design of the chip, rather than the assemblies. Therefore, the content of the First Warning Letter clearly specified the potential infringers as Company A and Company B, excluding the Plaintiff. Consequently, it was natural that the First Warning Letter was not issued to the Plaintiff, and there is no circumstance as claimed by the Plaintiff that the Defendant violated the Principles or caused damage to the Plaintiff’s business reputation.
2. The Second Warning Letter: The IP Court clarified that the content of the Second Warning Letter demonstrates that Company B and its U.S. subsidiary’s products implemented the Disputed U.S. Patent 634. The Second Warning Letter included the content of the Disputed U.S. Patent 634, a comparative illustrative analysis between the Disputed Assemblies and the Disputed U.S. Patent 634. The Second Warning Letter also recommended that Company B and its U.S. subsidiary seek clarification on the matter. The IP Court emphasized that the Defendant did not claim in the Second Warning Letter that Company B and its U.S. subsidiary infringed the Disputed U.S. Patent 634, nor did it prohibit any actions by Company B and its U.S. subsidiary or specify any legal consequences for violations. Thus, it was determined that the Second Warning Letter was, in nature, merely a notification rather than a warning letter as defined in points one and two of the Principles, and thus the Principles are not applicable.
3. The Third Warning Letter: The IP Court determined that the Third Warning Letter merely reiterated the position stated in the Second Warning Letter without presenting any additional claims. Therefore, the Third Warning Letter is considered to be of the same nature as the Second Warning Letter, and the Principles do not apply.
However, based on the same factual background, the IP Court’s Civil Judgment (112) Min-Gong-Su-Tzu No. 1 dated December 26, 2025, filed by Company A against the Defendant, adopted a completely different viewpoint. Such judgment did not find that the Defendant’s issuance of the Second and Third Warning Letters constituted conduct inconsistent with the definition of issuing warning letters under the Principles. Instead, the IP Court's judgment recognized that the issuance of both Warning Letters was governed by the Principles, and the IP Court proceeded to conduct a further review. The judgment further pointed out that the Defendant’s Warning Letters (i.e., the Second and Third Warning Letters) enclosed the Disputed U.S. Patent 634 publication and an infringement comparison analysis, and clearly stated the content and scope of the patent application, the infringing products, the facts of infringement, and the infringement comparison. This evidence was sufficient to inform Company A’s end-brand manufacturers of the possibility that the Disputed U.S. Patent 634 might have been infringed.
However, in the Civil Judgment (113) Min-Gong-Su-Tzu No. 7, the IP Court held that the contents of the Second and Third Warning Letters did not allege patent infringement, nor did they prohibit specific actions by the recipients or indicate any illegal consequences. Therefore, the IP Court determined that the Defendant’s issuance of the Second and Third Warning Letters did not constitute the issuance of warning letter behavior as defined by the Principles. Despite the identical factual circumstances in both cases, the judgments resulted in completely different determinations. Whether this will subsequently affect the order of market competition remains worthy of further observation.