This chapter examines the autonomous migration of children, adolescents, and young people under the age of 18 in two border cities, Tangier, in northern Morocco, and Tapachula, on the southern border of Mexico. The world’s border regions are paradigmatic spaces and provide the basis for an analysis of the coordination of border regimes, the management of global mobility, and the dynamics of transnational capital. Unaccompanied child migrants are actors articulating new transnational mobility processes. The chapter begins with an analysis of both border regions. The border is regarded not only as a physical element but also as a process within countries, with its legal, procedural, technological, and ideological aspects all taken into account. The intersection between the European and North American migratory regimes and existing legal regimes for the protection of children turns unaccompanied child migrants into ambivalent legal subjects who are at once young people requiring protection and migrants to be controlled. Against the backdrop of this situation, the article examines the mobility processes of these subjects and the vulnerability they may experience. It also describes the actors who mobilize to control these subjects and those mobilizing to defend their rights. The article ends with a description of the work being done to defend the rights of child migrants by organizations in the two border cities (the Al Khaima Association in Tangier and the Fray Matías de Córdova Human Rights Centre in Tapachula) and the insights that these groups provide into the international paradigm for child protection through transnational social mediation. The work being done by the two organizations then leads to an examination of how to incorporate mobility into the protection paradigm promoted within the framework of international law and human rights.