I have never been able to figure out how to enforce the rules of my house and have kids and parents respect them. I am not speaking of my own of course.
So, I would do what any other parent would do.
Example if it was a language problem I would ask the child not to cuss or use in appropriate language in my house.
I would even mention it to their parents or at least the mom.
A few instance it never stopped. As a result I didn't let my kids have the other person over anymore.
Not what I really wanted. Just happened to be how it ended.
Something I always struggled with. Be Christian, understanding and it takes a village to raise kids.
If I would have only known that I would lose the family as a friend, but more importantly I would probably never be in the families graces again. It is a regret. Now that my oldest is a senior the time has gone by so fast I wish I would have found other ways to fix the issue.