A regulator in Germany has ruled that websites must only offer downloads of sexually explicit ebooks between 10pm and 6am.

Essentially, the euro nation's Youth Protection Authority has said 2002-era rules on protecting kids from blue movies on TV now cover digital books, publishing trade mag Boersenblatt reports. Telly stations in Germany can only broadcast X-rated stuff between 10pm and 6am; that now applies to raunchy ebook downloads, too, weirdly enough.

It stems from a complaint that a risqué autobiography titled Schlauchgelüste ("Pantyhose Cravings") was apparently all too easy for children to obtain.

It means erotic thrillers can only be fetched from the web late at night, Berlin time, unless the website hosting the material can verify the reader is an adult: Amazon.de, self-publishing authors et al will have to knock together some code that, pre-watershed, checks the age of someone before they can download a steamy ebook – or face the watchdog's wrath in Germany.

(What makes a book sexually explicit, or to use the regulator's words, "youth endangering"? A good question with no obvious answer.)

"It is not clear at this time how the ebook retailers will respond," notes book trade blogger Nate Hoffelder.

"Given the prevalence of adult content on websites outside of Germany, trying to control access on sites in Germany is just nuts. Even King Canute knew that he could not hold back the tide, but apparently German regulators lack that level of common sense."

As a result, pornographic titles will have to be registered as such so that websites can check against a database for ebooks to hide way until 10pm (1pm US West Coast time, and 4pm US East Coast time). Those who flout the law could be fined tens of thousands of euros in Germany. ®