I'm assuming he bought it with his own money. This may be a messy situation as telling users what they can and can't do with computers that they bought is never fun, "Oh by the way you can't have admin rights on your laptop anymore".
That's exactly the issue. However, laptops that use wireless are not allowed to join the domain. They pick up the wireless connection for Internet usage, but have no access to local network resources.

I've been thinking about breaking out network into subnets for a while now, and I just used this experience as a prime example to make the case for it to my boss. We also have a web server that I think should be sitting on a DMZ instead of right here on the main network with everything else.