My neighbours, the kids of which my kids play with, use a different system - their kids can earn screen time through compensatory good deeds (e.g. homework,chores, etc).
Different authorization schemes between interacting policy domains.
And there is the rub, both sets of kids are constantly back and forth between the households, knowing full well that the two sets of parents have been unable to agree on authorization policy and are consequently ripe for the screen-time picking.
Me to neighbour kid: Hey, are you allowed screen time?
Neighbour kid (with straight face): Oh yes.
Me to neighbour kid: Well I guess so ....
I suppose audit could help prevent the abuse. But, busy life etc.
I'm thinking of adopting a system in which, every time my kids went over to the neighbours, and vice versa, there was pinned to their shirt a note (signed & sealed) listing what they were NOT allowed to do.
<Forbidden action="pre-dinner snacks"/>
<Forbidden action="criticizing their Father's rules"/>
And yes, XACML.