
I would simply say to him something like this:
“Son …we can’t control you. If you really want to run away from home, we can’t stop you. We can’t watch you 24 hours a day – and we can’t lock you up in the house. But no one in the world loves you the way we do. That is why we have established these house rules. Because we love you, we can’t stand by and watch you do whatever you want – whenever you want – without any house rules. Running away from home will not make us change our minds about providing supervision and rules.”
Then it’s his choice to return home under your house rules or continue to attempt to manipulate you into changing your minds. A long as he is safe, I would just let him know that he is loved and that he can return home whenever he’s ready, and that he can take all the time he needs to make a decision. But he will have to follow the plan …period.
In the meantime, catch yourself feeling guilty – or feeling sorry for him – and remind yourself that you are fostering the development of self-reliance in your child. This is for his benefit – not yours.