The Japanese Ministry of Economy, Trade and Industry has now deemed importing of flash cartridges illegal, says Kyodo News. They had locked down the sale of 'Majikon' devices already, but now they're completely blocked from import, according to a translation by Kotaku.
As you can imagine, Nintendo pushed hard for this import ban. It's like DS piracy is the scariest thing in the world to them.
What would you do if importing an R4 or the like was illegal here in America?