Professor Volokh on voting by aliens:
I would probably be somewhat more opposed than my friend to letting noncitizens vote in state and federal elections, especially since in many jurisdictions noncitizens are a huge group, and I do think that swearing allegiance to your new nation is an important step in making people feel like they have a long-term stake in the nation's health. But it is important to realize that the proposals to allow noncitizen voting are not some departures from an unbroken American tradition.
For obvious reasons, we are at a peak in anti-alien feelings.
In fact immigration itself was unrestricted throughout much of our history. Immigration controls were non existent for the first 100 years of the Republic, reflecting the pro immigration stance of the Founders. Note that immigration is not mentioned in the Constitution. There is only a reference to naturalization and the requirement that the President be native born. Arguably, Congress lacks the power to restrict immigration since they are not given that power in the Constitution. It could be argued that immigration control is part of the inherent "police power" that all governments possess but that then leads to the question of whether or not the Feds have "police power" (outside of the Federal District) or if that is the sole province of the States.
Both advocates and opponents of immigration should keep in mind that two of the leading documents in the history of liberty include immigration among the rights that governments should respect:
The Magna Carta
[30] All Merchants (if they were not openly prohibited before) shall have their safe and sure Conduct to depart out of England, to come into England, to tarry in, and go through England, as well by Land as by Water, to buy and sell without any manner of evil Tolts, by the old and rightful Customs, except in Time of War.
The Declaration of Independence
He has endeavoured to prevent the population of these States; for that purpose obstructing the Laws for Naturalization of Foreigners; refusing to pass others to encourage their migrations hither, and raising the conditions of new Appropriations of Lands.