It is rare for anyone to say that I have responded temperately to anything, so I owe Jeff my gratitude. Jeff has also done a fine job of chewing over what is really the most troubling part of my Scene colleague Tim's post. This is where he describes race and place of birth to be equally morally "arbitrary." They are therefore irrelevant in determining the obligations owed, and an unjustifiable basis on which to distinguish between people as a matter of law.
The argument against legal discrimination according to race holds that depriving someone of fundamental legal and civic rights on account of an "accident of birth" is unjust. Similarly, slavery, which Tim invokes in his post, is the complete deprivation of legal personhood based on either some contingency (e.g., being captured and sold) or an "accident of birth." Both involve a denial of something fundamental that cannot rightfully be denied someone on such a basis. Place of birth, on the other hand, is substantially different. (Leave aside for now that this line of argument, if consistently maintained, would make birthright citizenship--one of the shibboleths of pro-immigration advocates--entirely unjustifiable.) First of all, there is no act of depriving someone of anything that is rightfully owed to him. There is no "right to immigrate," and so there can be no injustice in denying someone entry on the basis of origin and nationality. There is no question of force or coercion being used to "keep" someone in his home country, but simply in preventing entry into our own.
To be born in a place entails a connection to the people who live in that place, and everyone owes his particular good or ill fortune to his place of birth. This creates a bond of obligation between a person and his country that even precedes his civic obligations to the polity of which he and his family are members. Having a common country of origin with others necessarily implies affinities with and greater obligations to those countrymen. This is not only natural, or rather instinctive, in the sense that it is a common, instinctive coping and survival strategy, but it is also moral in that in entails a recognition of mutual obligations to those who generally share a place of origin. A common place of origin has created a relationship between people prior to their decision to associate with one another. It has made them fictive brothers and sisters before they have ever met. Note that the fictive kinship of shared origin is not necessarily forever closed, since a kind of adoption is always possible, but the offer of adoption and the response of oikeiosis (appropriation) are neither automatic nor freely given to just anyone, but must be earned.
In turn, privileging your countrymen is a fulfillment of your duties towards those to whom you are more closely related. Applying a different treatment to foreigners who wish to become a member of the polity is a necessary consequence of the obligations created by origin and through relationship with compatriots: just as we here owe something to the land that bore and nourished us (to use slightly romantic rhetoric for a moment) and have a relationship and duties to those who are from the same place, so the foreigner must have the same obligations to his country and compatriots. To fail to distinguish between compatriots and foreigners is thus a failure to recognise the different sets of obligations that both have to their respective places of origin; to erase the difference in treatment is to deny those obligations, which is itself a kind of impiety. It is in this way contrary to nature, and indeed wars against natural affinities.
It is strange that no one pushes this to another extreme: being born to two parents is unchosen, the "accident of birth" itself, yet we do not (at least if we are serious about the importance of family as the foundation of social organisation) deny that this "accident" entails a whole host of moral obligations of parents to children, children to parents and siblings to one another. The sungeneia (kinship) that binds us to our immediate blood relatives by the same principle binds us to our compatriots in our shared place of origin. The "kinship" with our compatriots is fictive, because it is not a literal familial connection, but it is real enough inasmuch as it refers to common origin. Ultimately, the argument that Tim and others sympathetic to his view are making is that where we come from is an irrelevant consideration, or is at least irrelevant enough not to merit being instituted in law, when origin is one of the most vital parts of a person's identity and an inescapable part of answering that most important of philosophical questions, "who am I?" This is just as true for those who have the relative misfortune of being born in poor, badly governed countries as it is for those who have been blessed with the fortune of being born here. At bottom, ending what Tim somewhat melodramatically calls "international apartheid" means denying that place of origin and nationality have any moral significance, when they typically do have moral significance for everyone.
To encourage people to write off their own countries as lost causes, as the mass immigration-to-reduce global poverty argument urges us to do, is to encourage them to neglect their obligations to their land and to their compatriots, even as it is an attempt to deny our own obligation to privilege the interests of our countrymen. With this proposal, we are confronted with moral failures upon moral failures: it is a summons to others to act impiously, while committing impiety ourselves. Nothing good can ultimately come from it. It is telling that those immigrants who do not neglect their obligations to their home country and their relatives back home, and who have come here primarily to make a living for the benefit of their folks at home, are necessarily among the least desirable immigrants from the perspective of the native population, since they have the fewest reasons to remain and assimilate.
Their "contribution," if you like, to the country is very limited, while the costs imposed while they are here tend to outweigh these benefits. (This is exacerbated by those who came here with no original intention of remaining permanently, but who are now unwilling to risk returning home--such is the ridiculous situation arising from marginally improved border security and virtually non-existent internal enforcement.) These are also going to be among those most likely to evade the legal procedures for immigration, because this entails costs of time and money that they cannot afford and are unwilling to pay. In this sense, the immigrants who are acting most morally with respect to their own countries and in keeping with their original obligations are the worst immigrants from the perspective of the interests of the host country, which means that it is actually part of the duty of the native inhabitants, out of their own obligations to their country, to arrange the laws on immigration in such a way as to discourage such temporary migrants from coming. To the extent that the native inhabitants wish to have a steady stream of new settlers, it is those who wish to settle permanently and adopt local habits who should be encouraged. This, of course, requires far more control over who comes into the country, rather than less.