There are two types of boundaries. Firstly, there are boundaries where I state what I'm (not) willing and able to do. Then there are boundaries that involve the regulation of others' behaviour.
Although there are exceptions, the latter generally involve this procedure:
- State the boundary
- Leave it to the other person to respect it ... or not
If they push back, argue, negotiate, question, or are snippy or accusatory, ignore it. They're spoiling for a fight. Let them have the last word, because, if they do, that is what they will remember. If they're reflective, they'll see what they're doing. If they're not, pointing it out won't help.
This keeps my hands clean. It's OK to make polite requests, and it's OK not to fight to the death over them.