Which address would resolve differently, depending on which DNS server
you're talking to?
I'm not sure that's good enough; being able to identify the *network
ingress point* is the thing I'm after. For wired connections, that's
the access concentrator, for wireless ones, the nearest tower.
It would be necessary to be able to tailor the response to the inquiry
based on that, I think, to fulfill the requirement *I'm* trying to
fulfill in this posited design -- which is not guaranteed to be the
same as any possible regulatory requirement.