I will jump in and try to answer this question. He talks about free will in the beginning of the book. We do have the free will to self intoxicate ourselves, and he says if that's what you want then go for it! So now let's assume that you don't want to drink anymore. The BP is a self inflicted removal of that choice. I will never drink again, and I will never change my mind. No matter what. It is taking away that freedom to self intoxicate that you freely impose on yourself. And yes it is binding and for life. You no longer are free to get wasted. I guess there is nothing stopping you from breaking that solemn oath, but if you did it would mean you never really meant it. Your word to yourself would be worth mud and you would be nothing more than a slave to your addiction. A Beast only interested in one thing and not a human being with integrity and self control.