International migration yields pervasive cross-border social engagements, yet homeland political involvements are modest to minimal. This contrast reflects the ways in which the distinctive characteristics of expatriate political life impede participation in the polity that emigrants have left behind. As polities are bounded, moving to the territory of a different state yields political detachment: diminishing awareness of home country political matters and weakened ties to the home state's electoral institutions. To assess this argument, we use a representative survey of the Mexican-born population in the United States to analyze two critical conditions for participation in expatriate elections: emigrants' ability to demonstrate eligibility to vote and their knowledge about voting procedures. We find clear signs of detachment. Most Mexican emigrants are not in a position to participate in homeland politics. Social ties, while pervasive, are associated with more knowledge only for the very small segment of the most engaged.