Nintendo's blocking of mature content on the European Wii U eShop at select times of day is due to German laws restricting the sale of mature content, the company confirmed with Polygon today.
European Wii U owners can only purchase content that is rated PEGI 18 between 11 p.m. and 3 a.m. (10 p.m. to 4 a.m. CET in Germany), including games like ZombiU and Assassin's Creed 3. Nintendo has confirmed that the eShop is held to Germany's content regulations because its European branch is based in the country.
"At Nintendo we always aim to provide a safe gaming experience for fans of all ages and ensure that we comply with applicable legal age restriction requirements across Europe," said a representative for Nintendo.
"Since Nintendo of Europe is based in Germany, Nintendo eShop is complying with German youth protection regulation which therefore applies to all our European markets. Under German law, content rated 18+ must be made available only at night."
A representative for Nintendo of America told Polygon that the policy is Europe-only and does not impact the North American Wii U eShop.
Polygon has reached out to Nintendo for additional details and will update this story with more information as we have it.