It's a parody.
The author, Sandrovich, has a history of specifically choosing real-life people and then changing letters in their names to fit his fictional parody. Including tv shows, films, etc.
[ul]Russian President Putin = President Petin
Jason Statham = Jason Sgatham
Arnold Schwarzenegger = Harnnold Dogegenchonegger
U.S. President Obama = President Mobama
Last Action Hero = Last Action Star
Conan the Barbarian = Conan the Red Bull
Twins + Kindergarten Cop = Twin Cops[/ul]
He does it frequently, even when the reference is blatantly obvious. It would therefore be more out-of-place in context to the fictional manga to translate ルール (Rūru) as the actual person, "Rühl." Instead, "Rule" "Rool" or "Rewl" would be more consistent.
I know. It's meant to be different from his real-life name. Otherwise, it's not a parody. It'd (potentially) be libelous.