The Japanese Ministry of Economy, Trade and Industry has announced an import ban on Nintendo DS flash carts, according to Japanese site 47News (translated via Kotaku). The flash carts allow users to play pirated game on their DS systems, and have been a big problem for the Nintendo in the region.
The sale of the R4 flash carts in Japan has been illegal since 2009. Nintendo has been fighting a war against the devices worldwide, with similar bans being instituted in the UK, Italy, Spain, France, and Taiwan. Legal cases against specific distributors in Australia, Germany, and the UK have also been wins for Nintendo.
Selling the thing at all doesn't seem to be a winning strategy these days.