The post is a couple of days old, but Tim Lee goes into some detail here spelling out the common-but-odd view that stepped-up immigration enforcement somehow “can’t work.” Now, if you take “working” to mean that zero people will be residing illegally amidst a large, demographically diverse country of 300 million then, sure, it’s probably not feasible to do that.
At the same time, as Tim says the reason people immigrate here illegally is that there’s a lot to be gained by immigrating illegally to the United States. And the reason people employ illegal immigrants is that there’s a lot to be gained by employing illegal immigrants. But by the same token, if we take measures to increase enforcement the measures don’t need to be 100 percent effective to raise the cost (or decrease the benefit) of immigrating illegally and thereby reduce illegal immigration at the margin.
Now, I don’t really think we have too many immigrants in the United States (though I’d prefer to see a higher ratio of legal to illegal immigrants) so I like the conclusion that enforcement is futile, but there’s no real reason to think it is.