The adult games curfew, which affects games such as ZombiU, was spotted by a NeoGAF user, who after contacting Nintendo was told that adult content would only be sold between 11pm and 3am.
"Dear customer, we would like to let you know that Nintendo has always aimed to offer gameplay experiences suited to all age groups, observing carefully all the relevant regulations regarding content access that are present in the various European countries," reads the Nintendo statement.
"We have thus decided to restrict the access to content which is unsuitable to minors (PEGI) to the 11pm - 3am time window."
Users attempting to buy restricted content on systems on which no parental controls have been set are met with a message informing them of the block, reading: "You cannot view this content. The times during which this content can be viewed have been restricted."
Copyright: NintendoEarlier today it was revealed that the Wii U has grossed more money than the original Wii, despite selling fewer units.
Official North American sales records show that Nintendo shifted more than 425,000 Wii U consoles during its first week on sale, falling short of the Wii's 475,000 sales, but grossing approximately 21% more cash.
The console reportedly shifted 40,000 units during its first weekend on sale in the UK, with supplies said to be limited until after Christmas.
Despite the impressive figures, no Wii U games made this week's all-format top ten.
> Read our review of Nintendo Land
> Read our review of New Super Mario Bros U
> Read our review of ZombiU
> Read our review of Scribblenauts Unlimited (US only)
Watch a hands-on video with the Wii U below: