Demanding that the law of a country should be followed by another is totally no sense. They can agree, make agreements about it, and even take legal action to the Highest court, so it could be evaluated, but using your nationality as an argument of what you can do, it's just plain wrong.

This is nuts. How can anbody be expected to both know that you’re German and German law when you post on an international website?

Or is this a German law that exists to prevent other Germans from doing things but that the rest of the world scoffs at?

https://choosealicense.com/