He needs to decide his boundaries. A lot of people have no idea what their boundaries are, or even what it means to enforce boundaries. It is one of the links in the post Cadet gives newcomers. He needs to study it. Decide what principles he can not live without having these honored in his life. Decide what he will not tolerate in his life.
Boundaries are not to be used to police the other person's life. It is to protect him. If the other person crosses that line he has around him for protection, then it is a direct attack on him. It may be rather subtle, or it may be daring.....but they have crossed the line. Now, what will he do about it? Slug it out? No, I don't mean anything physical. What else can he do? Since he cannot control the actions of the other person, then that just leaves him doing the action. Here's the catch......if his action does not cause some type of consequence for the other person, then it is not an effective boundary.
And an ineffective boundary is no boundary at all. He needs to know, in advance, what his actions will be, if his boundary is dishonored........then by all means, know he can carry it through.
He should never make some brave statement and then back away when tested. B/c believe me, the WW is going to test those boundaries, so he needs to suit up his armor every single day.
"What is best for my kids is best for me" Amor Fati Link to quotes: https://www.divorcebusting.com/forums/ubbthreads.php?ubb=showflat&Number=2879712