But, yer Honor ...
"She was naked and unconscious ... she didn't object, and she doesn't even remember it ... how can I be guilty?"
If you're calling yourself smart enough to know the difference between an unsecured and a secured access point, you know better than to claim, "But yer Honor ... it was open and defenseless, and it didn't even know I did it ... how can I be guilty?"
And, no, DHCP assigning an IP is not explicit permission to access that node.
And, no, DHCP wasn't designed the way it was to give you unauthorized access to somebody else's router.
And, yes, consumer-level wifi access points/routers ship unsecured because the general population is, oddly enough, not very technically inclined, but again, this is not explicit permission to tap into them.
THE UK/US LAW IS: Thou shalt not piggyback on someone else's bandwidth without their explicit permission. Period.
I hope that's not too complex for you guys ... you don't like it, lobby to get your laws changed. Sheesh.