It's definately his own car, he pays the insurance and for all the petrol? If so surely there's no grounds for his parents to stop him taking the car and he should go anyway, parents be damned. Of course this could lead to serious meltdown at home so I guess he would have to explain that calmly and rationally, however if he doesn't pay full insurance or full petrol (and road tax? I know we have road tax do you? ) if his parents pay anything towards that car, they have a say in the matter and he might be boned.
Oh and what's with you getting negged? You been somehow pissing people off?
When I was 19 I told my dad I wanted to drive from South Carolina to Canton, Ohio by myself in the middle of winter with no snow driving experience. He said, "Ok, just drive safe," and that was the end of the conversation. There might be more at work here than what we know,