I see real problems with laws such as that. Unless they have a requirement of payment or a purchase, they simply opened their system for use. If they do not take any means to restrict people not given permission to use their system, I see it as a failing on the business' part.
in the situation with your relatives, the neighbor is not intentionally allowing people to use his system. With the coffee shop dude, they intentionally opened their system to use. There are means to prevent users not authorized from using the system and if those means are employed and somebody hacks into the system, then I can see the crime. If it is simply an open system intended to provide free service for the public, then I see no crime.
and here is a quote from the coffee shop owner:
In the story, the coffee shop owner said the man could have come inside and used the wireless connection for free.
I know this is not the same but that would be comparable to arresting a guy setting outside the store near a window for using the light from inside to read his book. If you do not charge for it and you allow "it" to escape your walls, I do not see how you could prosecute somebody for using it.
so, what happens if a guy is inside using the system and leaves his computer on when he leaves. If there are any transmissions to or from his computer to the system once he has walked through the door, has he now broken the law?