A British man has been arrested for connecting to someone else's unsecured wireless network without permission. According to BBC News , police saw the man using his laptop outside a house in a London neighborhood. When they asked him what he was doing, he admitted to surfing an open wifi network and they took him in. “Dishonestly obtaining electronic communications services” is an offense under Chapter 21 of the UK's Communications Act 2003
Whether using open wifi networks is illegal on this side of the pond is much less certain. The closest law on point is the Computer Fraud and Abuse Act, which was written in 1996 in response to the threat of computer hacking rather than wardriving. That Act makes intentionally accessing a computer without authorization a crime under certain circumstances, most of them related to information obtained by such access. Some people have already been arrested in the US for using open wifi networks, but those cases haven't made it before precedent-setting courts yet.
There are many passable analogies for why a person should be able to use an unsecured network (for example, it's like someone else's sprinklers sending water onto your lawn), but most of them fail at the crucial point that you're not just accepting the signal that's broadcast out from the access point – you're also sending data back, even just browsing the net, in the form of url requests. On the other hand, if you're communicating with the router and it's accepting the packets you send it, maybe that's as much authorization as you need.
Thumbnail photograph courtesy of Jacob Bøtter .