Eligibility for Declaratory Judgment Action in Japan

2021.08.28
Aki Ryuka
Japan Patent Attorney
Attorney at law, California, USA


A declaratory judgment (DJ) action can be filed, only if the plaintiff has an interest in the lawsuit. Whether the interest is found well depends on the warning letter.

DJ Actions Denied
Takai v. Yanagiya Machinery Co.,Ltd. (IP High Ct., October, 2014)

– The patentee merely suggested that the subject product might fall within the scope of the patent, but did not show any interest in enforcing an injunction against the plaintiff.
– There was no existing dispute between the parties, and there was no real and specific risk
that threatened the right and legal position of the plaintiff.

DJ Actions Accepted
Anonymous Plaintiff v. Systech Kyowa Co.,Ltd. ((IP High Ct., June 2007)

– The patentee sent warning letters to the plaintiff and its business partners.
– The business partners considered the plaintiff’s product infringing the defendant’s patent and terminated the sales agreement.