Foreign Statements Weighed for Estoppel by Japan’s IP High Court

In a possibly consequential decision, the IP High Court overturned the Tokyo District Court’s infringement case decision against Debiopharm International S.A., judging that plaintiff Nichi-Iko’s patent No. 4430229 was not infringed. What was important about the decision was that the IP High Court applied the principle of estoppel to statements made overseas, taking into consideration Nichi-Iko’s foreign patent prosecution on the same invention. This is in spite of the fact that customarily Japanese IP courts have not accepted foreign statements as basis for estoppel.

As each country’s patent office and patent laws vary, it makes sense that as patent claims need to fit local practice in each jurisdiction, legal procedures may vary depending on how those procedures are carried out locally. Japanese procedure has tended toward limiting the statements it would consider, to those made in Japanese prosecution, perhaps expressing a sense that Japan has unique and particularly high standards. On the other hand, in countries like the United States of America, estoppel has been considered based on statements made in other countries.

A sort of Japanese procedural exceptionalism may have protected litigants in the past from drawing on foreign statements, but that may no longer be the case. Applicants and litigants in Japan will need to consider more carefully the arguments they make globally, and what statements their opponents may have made overseas.


Heisei 28 (Ne) 10111.

(The information provided on this website is for informational purposes only and is not intended as legal advice. For questions or inquiries, please contact us for more information.)

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