Despite the fact that family unity is a core goal of the US immigration system, various US immigration policies prolong and force family separation. This paper examines the process by which Mexican binational families assert their legal rights to family unity through the mediating role of Mexican consulates. The paper analyzes an administrative database within the Mexican consular network that documents migrant legal claims resulting from family separation (particularly child support and custody claims), along with findings from 21 interviews with consular staff and community organizations in El Paso, Raleigh, and San Francisco. It finds that the resolution of binational family claims is, in part, dependent on the institutional infrastructure that has developed at local, state, and federal levels, as well as on the capacity of receiving and sending states and the binational structures they establish. The paper recommends collaboration in identifying areas of strengths and weaknesses within consular networks; development of formal protocols for consular staff and officials to work with government agencies, nongovernmental organizations, and lawyers in resolving legal claims; limiting the role of local officials in the enforcement of US immigration law; and sharing the best practices of the Mexican consular network with consulates from other countries.