I am the step parent of a 17 year old boy. He is a sweet, funny, and smart kid, but has no discipline in his life. He skipped school so much last year that he failed some classes. He signed up for summer school "online" but then never completed it. We have caught him in numerous lies over and over again. He is waiting to hear if he is going to be charged with a felony. A friend of his and he decided it would be a funny joke to tie a girl friend of theirs up to a pole and throw water on her. The girl's mother did not think it was such a funny joke, hence she pressed charges.  
He came to live with us last year for 3 months. It was a struggle every single day. When we were finally getting somewhere with the discipline, he asked his Mom if he could move back and she let him! 
What do I do as the step-parent? I have virtually no "control" over the decisions made regarding him, but I have to suffer the emotional and financial consequesnces of his lack of discipline. My husband is reluctant to discuss this with his ex in any great length because she becomes defensive and angry when he does. He left her for me after we met on the internet. She is not our biggest fan, but we have managed to be cordial and have talked briefly a few times.  
My upbringing was pretty strict, and it drives me crazy that my husband and his ex can't see that their lack consistency in discipline is the number one contributor to their son's current and future demise.  
Please help! Any advice on what I should do would be appreciated. I am tired of being the heavy, but I know someone has to be. 
Thank you.