¹ See Carens, Joseph, “Aliens and Citizens: The Case for Open Borders,” Review of Politics 49 (Spring 1987), pp. 251–73CrossRefGoogle Scholar; and Carens, Joseph, “Migration and Morality: A Liberal Egalitarian Perspective,” in Barry, Brian and Goodin, Robert, eds., Free Movement (London: Harvester Wheatsheaf, 1992), pp. 25–47Google Scholar.

² Walzer, Michael, Spheres of Justice (New York: Basic Books, 1984), p. 61Google Scholar.

³ For attempts to shield states from external criticism of their immigration policies, see Walzer, Spheres of Justice; and Meilaender, Peter C., Toward a Theory of Immigration (New York: Palgrave Macmillan, 2001CrossRefGoogle Scholar).

⁴ It may no longer be purely self-imposed. Meilaender cites evidence in support of the view that there is actually an emerging norm in international law that requires this. See Meilaender, Toward a Theory of Immigration, pp. 280–81. But even if this is a norm, it is one that has emerged from practice and so it does not really change the question in the text.

⁵ Meilaender, , Toward a Theory of Immigration, p. 182Google Scholar.

⁶ Motomura, Hiroshi, “The Family and Immigration: A Roadmap for the Ruritanian Lawmaker,” in Hailbronner, Kay, Martin, David, and Motomura, Hiroshi, eds., Immigration Admissions: The Search for Workable Policies in Germany and the United States (Oxford: Berghahn Books, 1997), pp. 79–119Google Scholar.

⁷ Joppke, Christian, Immigration and the Nation-State: The United States, Germany, and Great Britain (New York: Oxford University Press, 2000Google Scholar).

⁸ This oversimplifies things a bit because in a few key source countries (Cuba, the former Soviet Union, Vietnam, Haiti in the early 1990s) the United States has set up a process for determining whether people would qualify as refugees and for accepting them for resettlement even before they have left their country of origin. Although such people do not technically meet the Geneva Convention definition of a refugee (which must be someone outside his or her home country), both the United States and the countries of origin in which these programs have been established have found this a more orderly way to manage a refugee flow that they anticipate would otherwise occur in a clandestine fashion. However, the United States never treats these programs as policies that it is morally obliged to pursue and certainly never suggests that any particular refugee has a moral right to be admitted to the United States.

⁹ Singer, Peter and Singer, Renata, “The Ethics of Refugee Policy,” in Gibney, Mark, ed., Open Borders? Closed Societies? The Ethical and Political Issues (New York: Greenwood Press, 1988), pp. 111–30Google Scholar.

¹⁰ Ibid., p. 120Google Scholar.

¹¹ For a fuller development of this argument, see Carens, Joseph, “Refugees and the Limits of Obligation,” Public Affairs Quarterly 6, no. 1 (1992), pp. 31–44Google Scholar.

¹² Abella, Irving and Troper, Harold, None Is Too Many: Canada and the Jews of Europe, 1933–1948 (Toronto: Lester and Orpen Dennys, 1982Google Scholar).

¹³ It is possible to construct more than one category, of course. For example, one can give some refugee claimants a more limited form of protection than others. See Joseph Carens, “The Philosopher and the Policymaker: Two Perspectives on the Ethics of Immigration with Special Attention to the Problem of Restricting Asylum,” in Hailbronner, Martin, and Motomura, eds., Immigration Admissions, pp. 3–51. Adding categories does not change the fundamental problem raised by the need to draw lines across a continuum, however.

¹⁴ Shacknove, Andrew, “Who Is a Refugee?” Ethics 95 (January 1985), pp. 274–84CrossRefGoogle Scholar; Zolberg, Aristide R., Suhrke, Astri, and Aguayo, Sergio, Escape from Violence: Conflict and the Refugee Crisis in the Developing World (New York: Oxford University Press, 1989Google Scholar); and Martin, David, “The Refugee Concept: On Definitions, Politics, and the Careful Use of a Scarce Resource,” in Adelman, Howard, ed., Refugee Policy: Canada and the United States (Toronto: York Lanes Press, 1991), pp. 30–51Google Scholar.

¹⁵ Brimelow, Peter, Alien Nation: Common Sense about America's Immigration Disaster (New York: Random House, 1995Google Scholar).

¹⁶ Borjas, George J., Friends or Strangers: The Impact of Immigration on the U.S. Economy (New York: Basic Books, 1990Google Scholar); and Borjas, George J., Heaven's Door: Immigration Policy and the American Economy (Princeton: Princeton University Press, 1999Google Scholar).

¹⁷ Brimelow, , Alien NationGoogle Scholar.

¹⁸ For a critique of that discourse, see Carens, Joseph and Williams, Melissa, “Muslim Minorities in Liberal Democracies: The Politics of Misrecognition,” in Bauböck, Rainer, Heller, Agnes, and Zolberg, Aristide R., eds., The Challenge of Diversity: Integration and Pluralism in Societies of Immigration (Aldershot, U.K.: Ave-bury Press, 1996), pp. 157–86Google Scholar.

¹⁹ Israel's Law of Return presents a special case here because it employs a criterion that might be regarded as a hybrid of ethnicity and religion. This case involves so many other complex and contested issues that I cannot pursue it here.

²⁰ Kanstroom, Daniel, “Wer Sind Wir Wieder? Laws of Asylum, Immigration, and Citizenship in the Struggle for the Soul of the New Germany,” Yale Journal of International Law 18 (Winter 1993), pp. 155–211Google Scholar; and Barbieri, William, Ethics of Citizenship: Immigration and Group Rights in Germany (Durham, N.C.: Duke University Press, 1998Google Scholar).

²¹ Rubio-Marín, Ruth, Immigration as a Democratic Challenge: Citizenship and Inclusion in Germany and the United States (Cambridge: Cambridge University Press, 2000CrossRefGoogle Scholar).

²² Kanstroom, , “Wer Sind Wir Wieder?”Google Scholar