Surely it works both ways?
Surely any WiFi router that broadcasts an SSID is making an unauthoriised access to your computer, in attempting to create a network between it and your laptop. So if I am prosecuted for using someone's WiFi, shouldn't the owner of the Router be prosecuted for "causing *my* computer to perform a function with intent to secure access to any program or data held in *my* computer".
If responding to a someone person's router's SSID invitation to join a network is illegal, then asking my computer to join in the first place is also an illegal access to MY computer!!!
Anyhow, technical arguments aside, it would appear that the main motivation behind these prosecutions is that the government is worried about the implications of people "stealing" bandwidth (i.e. the possibility of it being used for criminal purposes), so it would make MUCH MORE SENSE to change the law to make owners of wireless routers responsible for securing them, rather than prosecuting people for using them - especially in previous cases where the question of authorisation has been more ambiguous (internet cafes, etc).