If you use a German registrar you agree that the contract is governed by German law and in this case Joker.com complied with the judgement... why would they fight?
The German law is fucked up when it comes to the Internet... in many cases the reason for strange decisions is that the judges don't have a clue and many judgements are appealed successfully.
One Example:
http://news.bbc.co.uk/1/hi/world/europe/524951.stm