Fragmentation of Power and the Emergence of an Effective Judiciary in Mexico, 1994-2002

Legal reforms that make judges independent from political pressures and empower them with judicial review do not make an effective judiciary. Something has to fill the gap between institutional design and effectiveness. When the executive and legislative powers react to an objectionable judicial decision, the judiciary may be weak and deferential; but coordination difficulties between the elected branches can loosen the constraints on courts. This article argues that the fragmentation of political power can enable a judiciary to rule against power holders' interests without being systematically challenged or ignored. This argument is tested with an analysis of the Mexican Supreme Court decisions against the PRI on constitutional cases from 1994 to 2002. The probability of the court's voting against the PRI increased as the PRI lost the majority in the Chamber of Deputies in 1997 and the presidency in 2000.