One last note, I swear...

Hopefully ending my comments on this topic, if I were to write a web spider to go follow HTTP links, and download any images it found, would I be responsible if it downloaded child pornography? I would bet I would be in court. Why? Because I delegated my authority to a software agent acting on my behalf, and I am responsible for its actions. (unless you can argue common carrier status)

So how is this different than delegating control of who accesses your network to your wireless router? It is still an agent acting on your behalf, so if someone requests an IP address, and it gives it to them, then you allowed them access!