The citizens of that state seek to protect themselves and their property from crime and from ethnic and welfare spoils mandated to illegal aliens and their offspring by federal law. Arizonans' personal and property rights in this context take moral precedence over foreigners' rights to migrate freely to Arizona, Peikoff concludes.
To take the side of the Obama administration in this matter would be a betrayal of citizens who have acted, within the means available to them, to curtail the violations of their rights. To take the side of the Obama administration in this matter would also be tantamount to actively aiding its long-term strategy of increasing the number of government dependents and diluting the strength of the opposition to Big Government.
Peikoff explains why restricting Muslim immigration is a proper defensive function of a government of a free society in another podcast segment.
UPDATE (May 5, 2013):Both segments are clipped, condensed, and presented in this video: http://www.youtube.com/watch?v=jr1fMOJTfM4&feature=player_detailpage#t=150s