I’ve been researching this issue, as it comes up in most discussions regarding PAWS. The best article on the topic by far is:

D M Síthigh, “Law in the Last Mile: Sharing Internet Access Through WiFi”, (2009) 6:2 SCRIPTed 355 [pdf]

Also interesting is Martin Varsavsky‘s, Founder of Fon, response to this discussion, on this blog