If this is indeed a firm boundary, and if it is to have any affect, then it would have to be clearly set prior to anything happening. I don't know how and if I should bring it up.
More thoughts...
I think right now a discussion like this would fall under the category of "Rocking the Boat"
We have already agreed that we aren't going to be having that sort of external relationships, so -- no point in bringing it up while Retro is 7 weeks away.
Me 42, W 39, S8, S6, S2 M 11y, A & ILYBNILWY 11/08 Walking away from a bad situation.