serious: Overhaul the nation's immigration system entirely. Make it easier for people to come here through the usual process, and reconcile those who are already here though other means. They come to America for a reason, often at large sacrifice-it's time to encourage, not discourage, this enthusiastic new blood into our country.
non-serious: Force all libertarians into a sort of reservation where they can run their own government, but with the provision that no one can use the post a message to the world wide web or usenet EVER. When the reservation descends to anarchy, the borders will be sealed and the reality show TV rights sold to the highest bidder.