  There are several now classic defenses of state’s rights to control borders. David Miller (Miller 2005, 2007), Michael Walzer (Walzer 1983) and Christopher Wellman (Wellman and Cole 2011) have been particularly important. Joseph Carens is the most influential proponent of the alternative “Open Borders” position (Carens 1987, 2013, but see also Cole 2000 and Wellman and Cole 2011). While many theorists discuss the responsibilities to refugees and guest workers, Walzer’s treatment is particularly influential, especially in arguing for his view that guest worker programs are only justified when they offer such “guests” a proper pathway to full and equal citizenship (Walzer 1983).  Wellman offers comprehensive discussion of defensible admission criteria (Wellman and Cole 2011). Whether brain drain issues should be salient for migration decisions has been the subject of recent discussion (Carens 2013, Oberman 2012, Brock and Blake 2015). For detailed coverage of issues concerning whether borders should be more or less open, what our obligations are to refugees or guest workers, and issues concerning the ethics of recruiting  immigrants away from poor, developing countries, see the entry on  immigration.  