(((Lostsoul)))
Welcome to SR!
Did he make the choice to go into recovery, willingly? The reason I ask, is some people make that choice to get out of worse consequences.
As far as why he would still use, it's because he thinks he can get away with it. He may be wanting to convince others he's in recovery, but still wants what he wants.
As out to lunch said, nothing you do or say will make him use or not use.
The best thing to do is focus on you. If you don't like his behavior, make some boundaries and stick to them. I know it's easier said than done, but you don't have to put up with his behaviors if you don't want to.
Hugs and prayers!
Amy