Japanese trademark law is mainly enacted by the Trademark Act (商標法, Shōhyō-hō). Under this Act, only registered trademarks establish a "trademark" right (Article 18), and examination procedure is necessary for trademarks to be registered (Article 14). On the other hand, the protection for unregistered trademarks is provided by the Unfair Competition Prevention Act (不正競争防止法, Fusei kyōsō bōshi-hō).
English translation
The definitive version of Japanese law is the text in the Japanese language. An official English-language translation of the law does not exist, but the Ministry of Justice Japan has the website "Japanese Law Translation", where you can search for Japanese laws and their unofficial English translation. IP laws such as Patent Act, Copyright Act, Trademark Act, Design Act and Unfair Competition Prevention Act are included there.
In addition, J-PlatPat offers the public access to IP Gazettes of the Japan Patent Office (JPO) free of charge through internet.
Reliable information on Japanese IP law in English is also provided by the websites of Intellectual Property High Court, Japan Patent Office, "Transparency of Japanese Law Project", European Patent Office, and Institute of Intellectual Property (IIP) of Japan.