I think that there is a fine line here, as it does not say exactly what the person was doing with the Wi-Fi access. If the guy was just browsing the shared files, then he should not be punished by the legal system. On any network, any shared files should be expected to be viewed. Anything that the owner doesnt want shared should be kept private.
However, if the guy were using his access to the network to gain access to the internet, he should be charged and punished as the law states for stealing other utilities (water, power, cable, whatever else). Essentially, that's what he would be doing is stealing the internet utility.
The real gray area comes because information is broadcast over the airwaves. If the guy had a 500' Cat5 cable running from the base station to the SUV, this would be no problem whatsoever.
On a side note, it would be freaking halarious if they had a printer shared over the network and the guy started printing stuff to it.
"I'm watching you..."
"I know what you've been looking at..."
"All your base are belong to us."
HA!
