The Case for Getting Rid of Borders—Completely, by Alex Tabarrok, except for this part:
What moral theory justifies using wire, wall, and weapon to prevent people from moving to opportunity? What moral theory justifies using tools of exclusion to prevent people from exercising their right to vote with their feet?
No standard moral framework, be it utilitarian, libertarian, egalitarian, Rawlsian, Christian, or any other well-developed perspective, regards people from foreign lands as less entitled to exercise their rights—or as inherently possessing less moral worth—than people lucky to have been born in the right place at the right time. Nationalism, of course, discounts the rights, interests, and moral value of “the Other”, but this disposition is inconsistent with our fundamental moral teachings and beliefs.