I don't want to speak for Michael, but while he clearly states that he is particularly focused on policies that curtail one's right of movement, most of the points in his first comment apply as well to any policy intended to change incentives to move. Maybe it would be helpful to talk about a concrete policy question. One common case of a policy that curtail's one right of movement is restrictive citizenship policies. Many countries revoke the citizenship if individuals become citizens of another country. I think it is fairly clear that this curtails one's right of movement, by taking something away from people who move and acquire another citizenship. Under its new constitution, Kenya explicitly drops this policy and allows those who obtain another citizenship to remain Kenyan citizens. It is likely that this will increase the gross brain drain, i.e. more educated Kenyans will emigrate, knowing that if they become citizens of other countries they will not have to give up the benefits of Kenyan citizenship. The net effect on the supply of skills of Kenyans in Kenya, however, is uncertain, because the change may also increase the incentives for Kenyans to obtain skills, and also because more Kenyans may return. I wonder if Daniel would argue in favor of restricting dual citizenship to reduce brain drain? Or are there other policies he would propose?