NEW YORK (AP) — New York Mayor Michael Bloomberg is warning that a federal judge's ruling today could bring a return to the soaring crime rates in the city that were seen in the 1980s.

He says the judge doesn't understand "how policing works."

The judge today found that the city's police department has illegally singled out large numbers of blacks and Hispanics under its controversial stop-and-frisk policy. She appointed an independent monitor to oversee major changes in how that policy is carried out.

Bloomberg is vowing to appeal.

NYPD Commissioner Raymond Kelly says the notion that the police department engages in racial profiling is "recklessly untrue."

The ruling came in the case of four men who say police unfairly targeted them because of their race. There have been about 5 million stops during the past decade, mostly of black and Hispanic men.