Disputes about genetically engineered crops are linked to wider debates about the globalization of agro-food systems and its consequences for food security, social equity, and rural life.  Biotechnology expert discourse rarely addresses these wider issues.  An exception is the assessment of transgenic maize by the NAFTA Commission on Environmental Cooperation (CEC), which recommended a moratorium on Mexican imports of US-grown maize.  Controversy about 'contamination' of indigenous maize varieties by US-grown transgenic corn has been intensified by rising Mexican discontent with the terms of regional economic integration.  In this context, scientists and officials were pressured to consider not only risks to maize biodiversity but also the ecological, and cultural characteristics of maize in its Mexican settings and the implications of asymmetric power in North American agricultural trade.  In contrast to most narrowly-framed biotechnology risk assessments, the review took account of interventions by rural social movements.  While the new moratorium was not adopted by the state, continuing conflicts over GMOs in Mexico have blocked introduction of transgenic maize and have enlarged the political space for debate over Mexico's development direction.  These conflicts reflect the differing interests of various state actors and economic sectors with regard to trade liberalization.  They also reveal contrasting food-system paradigms: further agricultural modernization, export competition, and food-import dependence versus an alternative vision of revitalized rural life, farmers' rights, and national food sovereignty.