My guess is that it was illegal for them to go near Mars because there is no way to sterilize that roadster. We don't want Elon's microbes contaminating the pristine Mars environment I guess.
The final orbit goes out past Mars into the asteroid belt. It will loop back to Earth in a ~1.5 year orbit.
My earlier post on this very topic.
Not sure if you familiar with this stuff in space website, I just learned about it. You can track where the Tesla is, among many other satellites and debris. Just some FYI if you interested.
http://stuffin.space/?search=tesla%20roadster