The U.S. Justice Department says that issuing large fines and putting poor people in prison for not paying them is illegal. The law enforcement agency said putting people in jail or prison for not paying fines is unconstitutional. It damages trust in communities and local governments, it said. The Justice Department warning came after a conference in Washington in December. It revealed that some communities relied on fines as a source of revenue. The government found that fines and jailing happened frequently in Ferguson, Missouri. The small community near St. Louis was the center of attention in 2014. That year, street protests occurred after a policeman shot a black teenager to death. It was reported by multiple media sources that Ferguson’s court fines account for 20 percent of the city’s revenue. Fines were enforced for minor crimes like littering and speeding. Fines would reach over $500.