Would a "Prohibition argument" be relevant to the amount of immigration we should permit? Here's what I mean. Many people could argue the downside of alcholic beverages, as every woman who has been beaten by a drunken husband can attest, as every mother whose son was killed by a drunk driver can attest. Yet the illegality of alcoholic beverages did more harm than good, and most historians would say we rightly repealed Prohibition. We tried to prohibit something that couldn't rationally be prevented by legal prohibitions.
The restrictiveness of our quotas concerning immigration may be helping to cause a problem with illegal immigration. Prohibition empowered the Capone gang, the attractiveness of illegal immigration empowers the coyotes and drug cartels. Somehow, the situation in which we find ourselves makes breaking the immigration law desirable and attractive.
Jan Brewer likes to remind us all that we are a nation of laws. Of course we are. But the rule of law doesn't even guarantee that all violations of the law are morally impermissible. It could be argued that if someone comes across the border and does so intending to work for a living, pay taxes, and apart from the immigration law, to abide by the law, they may be doing what is at once illegal and morally obligatory. Unless you accept a moral theory that says it is always morally wrong to disobey the law, you have to consider this possibility. That is, we have a prima facie obligation to obey the law, but we also have an obligation to care for our families which may transcend the obligation to obey the law, and in the case of some illegal immigrants, they might have done what is illegal but morally obligatory. (Brewer thinks they're mostly here to run drugs and commit violent crimes, but what is the hard evidence for this claim? Why are they all in front of Home Depot looking for work, if they can get their money through crime?)
You know the old Emerson and Thoreau story? Thoreau went to jail for not paying taxes that would support what he took to be the unjust Mexican War. Emerson asked "Henry, what are you doing in there?" Thoreau answered "Waldo, what are you doing out there?"