A municipal police officer in Mexico's Zacatecas city holds up caution tape at the scene of a shooting. During decades of authoritarian government, senior federal officials quietly refereed between cartels. State and local authorities fell in line, accepting bribes to look the other way as heroin or marijuana flowed through their states. Mexico’s democratization has changed the equation. Now, local governments are more autonomous. Crime groups increasingly are seeking influence at the municipal and state level, through threats or bribery. The country’s precarious justice system has proved incapable of checking such graft.