In 1994, California voters approved Proposition 187, which prohibits provision of publicly funded education and social services to undocumented immigrants, and which requires public schools to verify the legal status of students and their parents. This paper examines socioeconomic and immigration trends leading to the emergence of Proposition 187, and challenges assumptions about its ability to deter undocumented immigration. Analysis of two cost-benefit studies in San Diego and Los Angeles Counties finds that they invariably overstate the negative fiscal impacts of immigrants on local and state governments and omit parallel computations showing that native-born residents have a larger tax use "deficit" than immigrants. Effectiveness of the proposition depends upon assumptions that illegal immigrants are not well integrated into society and could be easily deported, that education and social services serve as a magnet for immigrants, and that "illegal families" could be easily detected when they apply for services. A social science literature review shows that labor migration is a social process. Permanent settlement has been encouraged by social networks, changes in California labor markets, and worsening Mexican economic conditions. Undocumented workers residing in California have deepened their roots in their communities and are unlikely to go back to their countries of origin even if education were denied. Also, many families have a complex legal status and contain a mixture of U.S. citizens, legal residents, and undocumented persons. Finally, the"unstoppable flow" of undocumented immigration is largely the result of policies implemented by the U.S. and Mexican governments. Contains 63 references. (SV)