While I agree with Dr. Paul on most issues, I strongly disagree on immigration, and feel he is way out of line with a libertarian solution here.
The border fence is a ridiculous and horrible idea. Here's why:
1. You could build the Great Wall of China on the border and people will still get in here as long as the gov't is offering them a basket of goodies if they can make it to the other side- i.e. schools, hospital care, welfare, etc.
2. There is nothing wrong with immigration. Borders are an illusion. "Illegal immigration" is simply people moving from one location to another. We should not, nor should we want to, use the guns of government to police the situation. It's not libertarian and it's not even humane, it's just turning the guns on others, exactly what we as libertarians are against.
3. If the government builds a gigantic wall, it will eventually be used to keep us from getting out, rather than to keep brown skin folks from getting in.
4. The Canada border is wide open. Should we build a 3,000-mile taxpayer-funded fence up there too?
5. Who's going to pay for all this? Count me out. Will you force me at gunpoint to "pay my taxes" to fund this project?
6. Eminent domain (communism). In order to build the fence, the government will have to steal land from residents. How is this even the slightest bit liberty-promoting? This is pure communism.
The simple solution is to end the welfare-warfare state. No fence will be needed and immigrants will have to make it on their own with no government help or taxpayer funding.