THE JUSTICE Department said two things about Ferguson, Mo., last week, both of which should make Americans uncomfortable. First, federal officials announced that they did not have evidence showing that police officer Darren Wilson used unreasonable force when he shot African American teenager Michael Brown. Second, the department found that there is a lot of rotten policing with racist overtones in Ferguson. Mr. Wilson may have been exonerated, but that does not excuse the primed powder keg of community anger that Ferguson authorities had set in place before the incident occurred.

On the Michael Brown shooting, federal investigators pored through the local authorities’ evidence and gathered their own. After an exhaustive inquiry, they determined that they didn’t have a case against Mr. Wilson. They even punctured the widely circulated claim that Mr. Brown had his hands raised in surrender when Mr. Wilson shot him.This is the independent review of the event that Ferguson and the country needed, and it should serve as a warning to those who would rush to judgment in such sensitive policing cases before the facts are in order.

That is not to say that the protesters who filled Ferguson’s streets after the Brown shooting didn’t have a reason to be angry. The Justice Department found that they live under an official system consciously designed to suck money out of vulnerable people. The system combines high fines for all sorts of violations — such as $77 to $102 for having weeds or tall grass — and enforcement that too often is well beyond reason. Investigators found one instance in which a man sitting in a parked car was searched on bogus grounds, arrested for complaining about it, then ticketed for eight municipal code violations. The man claims the charges cost him his job.

Ferguson’s municipal court attaches more fees for missing a payment or a court date, and it regularly hands out jail time for failing to pay. One woman ended up owing more than $1,000 and spending six days in jail over parking tickets, and the court refused to accept the partial payments she attempted to make.

When Ferguson police go in search of revenue, the evidence the Justice Department found suggests that they target minority communities. Police and courts punish African Americans far out of proportion to their share of the town population. Add these numbers to the documented racial bias of certain city officials, the department concludes, “and there is evidence that this is due in part to intentional discrimination on the basis of race.”

Whatever the motives, the city’s approach is wrong and must change. Missouri politicians already are talking about abolishing the Ferguson Police Department. That may not be enough: The patchwork of tiny towns in the St. Louis area contributes to various municipalities’ need to raise revenues from fines and fees, so merging entire towns might help more. Assuming such fundamental reform is off the table, though, the Justice Department recommends a move toward authentic community policing in Ferguson, tracking and limiting racial disparities in policing, discouraging the use of force, providing clear information and simpler procedures to people before the municipal court, adjusting sanctions according to people’s ability to pay, and other long-overdue changes. Ferguson should not be the only town to listen.