It contains a legal brief alleging the ordinance is in conflict with the Japanese constitution, which the writer claims has been presented to the Tokyo district court.
I'm not sure about the procedures surrounding such a challenge so I can't comment as to whether it is actually valid; I have not heard any news regarding the matter in any case. Personally I'm not convinced the law can be challenged on constitutional grounds as it has been sneakily designed as a restriction on distribution to minors rather than an outright ban (although for practical purposes the effect is similar).