So, R4 cartridges. These are the devices that allow gamers to circumvent the security measure on a DS to run custom code — often referred to as homebrew — and illegally download copies of games. While the former reason often provides the grounds for defence of these cards, there are also a lot of people who used them to access dozens (possibly hundreds) of games to play for free, essentially stealing the content.
The cartridges have been illegal to import, advertise or sell in the UK since July 2010. In Nintendo's homeland, meanwhile, it's been illegal to sell the cartridges for three years, though the first arrest related to that law only took place this Spring. Meanwhile, it's been confirmed this week, by the Japanese Ministry of Economy, Trade and Industry, that it's now law that the devices can't be imported into Japan; this closes another loophole.
Nintendo was naturally at the forefront of lobbying efforts to enforce this import ban. Though it'll no doubt be a positive for the company, we can't help but feel that what seems like limited enforcement of the sales ban, and the delay before the banning of imports was formalised, mean that this change has come into effect after the damage has already been done.
At the moment there aren't any devices that do similar things on a 3DS, so it seems that the prominence of homebrew code and illegal game downloads on Nintendo handhelds is well and truly on the decline.