Mayor Michael Bloomberg filed a lawsuit on Tuesday to block a law allowing New Yorkers to sue the New York Police Department for biased-based profiling in state court.
The city says the law steps into an area already governed by the state.
It is one of two laws the City Council passed last month over the mayor's veto.
The other law passed creates an inspector general for the NYPD.
Both laws were meant to curb complaints about stop-and-frisk as well as other tactics.
In response to the lawsuit, Democratic mayoral candidate and City Council Speaker Christine Quinn issues a statement saying, "Mayor Bloomberg can sue all he wants, but at the end of the day, we will successfully beat back this ill-advised litigation and ensure the prerogative of the City Council to reform stop & frisk."