My position on immigration is fairly simple: I think we should allow more legal immigration, and we should make the process of obtaining citizenship (or at least a green card) less Byzantine than it is now. At the same time, we should make it harder to come into the country illegally. I don't think much of the fence, for both symbolic and practical reasons, but employer penalties and better border patrols are both demonstrably effective. Lower the price of legal immigration and raise the price of illegal immigration: that's the formula. Eventually you'll find a balance of costs that keeps illegal immigration at a low enough level that it's not worth spending more on. Then you're done.