Yes, I know it well - hates everything but his cell phone...ha.
The permission is what I was faced with too - my difficult child was in state custody for 6 months, because he accused husband of abuse and his DJO, who knows all, sees all, lol, was out-of-town, long story. Since I was going crazy dealing with his antics, and trying to keep up with his issues, and he was throwing everyone in constant turmoil, I finally had enough. Thankfully, I'd known since he was about 5 that you could drop this kid anywhere, any time, and he'd survive just fine. I was always rather proud of this perceived ability of his. Ha. And ha again.
So I said: you can choose to follow the rules, bide your time, save up money - which I was holding for him, as per a budget we drew up - and move out at 18 or go to the University as you say you want; or you can leave now. Choose wisely, make an adult decision and show me you have what it takes.
So he left. I didn't know where he was for quite a few days, altho I had my suspicions which did pan out. He'd left town. He's back, after a week, was here for 90 minutes and is supposedly saying with a friend about half a mile or so from home. No real idea, but since he dropped by today I know for sure he's alive and looks fine. Could use a haircut. Tried to get money for that too.