Yeah, technically - allowing 15-year-olds to tour without supervision would break any number of laws in several differing jurisdictions. Various, authorities could hassle you and eventually cause your parents considerable grief and legal expense. I can't think of any legal way to get away with it.

I think it is possible to apply for some kind of waiver so you could go on a long ride with pre-arranged consent and "emancipation" documentation, but again, that doesn't mean Sherriff Bubba can't pull you over anyway.....

PS - I rode my first overnight tour at age 14 - without any such "official approval."