I've heard this one before (not sure if I blogged or commented on it though), but strangely it is making a come-back. The bottom line is a law that makes any device that conceals the true origin of communication illegal. NAT anyone? :-)
Use a firewall, go to jail, and send Bill Gates too The Register: "'If you have a home DSL router, or if you use the 'Internet Connection Sharing' feature of your favorite operating system product, you're in violation because these connection sharing technologies use NAT. Most operating system products (including every version of Windows introduced in the last five years, and virtually all versions of Linux) would also apparently be banned, because they support connection sharing via NAT.'"