deleted_user: Correct, but it's illegal for the seller to sell it to Germans in Germany. At-least that is my understanding. So no the consumer is fine if they manage to get, but GOG as the seller is not.
PaterAlf: Yes, it's illegal to sell it for shops located in Germany. But GOG isn't. A German storefront doesn't make them a German shop.
The law was created at a time, where digital stores offering goods (or games to download in this case) simply didn't existed. That doesn't automatically imply, that they can get away with it.
If you or someone else believes so, come up with some precedences. The only ones I know of, are cases like
Dead Rising 2: Off the Record or
Wolfenstein: The New Order where they aren't allowed or had to be altered for Germany.
It's the same fallacy that everything digital = infos and informations should be free, therefor I should be able to get game / mp3 / whatever for free, just because the law didn't explicitly named it.
Demanding from GOG to step into potentially hot water, because the gamers in country X fail to take up their civil rights and battle it with the different available political tools their country provides, is borderline stupid.