I would suggest that with a child who is consistently doing this I would adjust my expectations and my response. Clearly he needs to step his toe on the line and get that serious response before he believes that it's a boundary and if he has any issues that make him feel insecure he will push it to feel better. I was watching a PBS show on monkeys last night and she showed that at a year they, according to her, "Seem to intentionally get themselves into spots that force their mother to come and rescue them," and I told dh, "Or the more brave among the children take the greater risks because they trust their mother to take care of them AND it's the most adventurous and bravest who will be the dominant males
"
I would be thrilled if he was doing it. I'd spend a season of saying it/making it happen and enforce the boundary big time