A unit of billionaire Hiroshi Mikatani's internet retailer, Kenko.com Inc announced the filing of a lawsuit against the Japanese government in its fight against restrictions on the online sale of some of the drugs in its portfolio.

The government ban, according to Rakuten Inc, is 'unconstitutional' in its lawsuit filed at the Tokyo District Court. This was confirmed by the unit's regulatory filing done yesterday, as a reaction to the Japanese government's plan to limit online pharmaceutical sales.

This comes after Mikitani, Rakuten's 48 year old head, had threatened to take legal action against the government. He also said he would resign from a position in a key government council should the Prime Minister moves ahead with the law that would prohibit the online sale of a number of pharmaceutical products.

In a press conference, Chief Cabinet Secretary Yoshihide Suga at a press conference said that the Kenko suit and the issue on online drug sales would be handled according to the law. He said, "It will be fought in the the lawsuit."

If Mikatani resigns, this would be a blow to the image of Prime Minister Shinzo Abe as he pushes his agenda for growth in the current session of the Japanese Diet. Mikitani is one of the leading entrepreneurs in Japan. When asked about the possible resignation, Rakuten spokesman Daisuke Nakane declined to provide any comment on the matter.

The Japanese Pharmaceutical Association had opposed the conduct of online sales as the group said it increased the risk of users experiencing side effects and contraindications. The Association represents 100,000 licensed pharmacists throughout Japan. 

Kenko.com in January had won in a lawsuit filed with the Japanese Supreme Court prohibiting the online sale of over the counter medication. Because of the government edict, Kenko lost nearly JPY500 million or USD5 million in annual sales or about 30,000 orders.