There are two ways in which rights and liberties, taxes and benefits can be rationed: by citizenship or by residency. Even in the USA, some benefits, such as compulsory education, emergency room health care, and so on are already rationed by residency, not by citizenship.
Many countries allow non-citizen residents to pay taxes into and in turn obtain other social programs, such as non-emergency health care. In most cases, new immigrants are relatively young working-age adults, whose education the receiving government did not have to pay for and who would pay more in taxes than receive benefits for a long time, even if they were entitled to exactly the same benefits as citizens. This makes eminent demographic sense for the maintenance of a social democratic state in a rich country, as the richer a country is, the fewer children its native-born citizens tend to have.
To make the rationing of rights and liberties, taxes and benefits, by residency rather than citizenship work globally, we can push for a multilateral agreement -- say, a General Agreement on Migration (GAM) -- in which all participating countries agree to allow immigrant residents to have many or all of the same rights and duties as citizens. You might say that's a very complex agreement, and it is, but we already have such multilateral agreements that have gone in the direction of treating all investors and corporations, regardless of their places of incorporation, the same. Surely, we can move in the same direction in treatment of people, but most (all?) rich countries in the world have gone in the opposite direction. But if the WTO, why not WMO (World Migration Organization)? -- Yoshie <http://montages.blogspot.com/> <http://mrzine.org> <http://monthlyreview.org/>