The U.S. Supreme Court on Monday declined to hear an appeal of a controversial Illinois law prohibiting people from recording police officers on the job.

By passing on the issue, the justices left in place a federal appeals court ruling that found that the state's anti-eavesdropping law violates free-speech rights when used against people who audiotape police officers.

A temporary injunction issued after that June ruling effectively bars Cook County State's Attorney Anita Alvarez from prosecuting anyone under the current statute. On Monday, the American Civil Liberties Union, which brought the lawsuit against Alvarez, asked a federal judge hearing the case to make the injunction permanent, said Harvey Grossman, legal director of the ACLU of Illinois.

Grossman said he expected that a permanent injunction would set a precedent across Illinois that effectively cripples enforcement of the law.

Alvarez's office will be given a deadline to respond to the ACLU request, but on Monday, Sally Daly, a spokeswoman for Alvarez, said a high court ruling in the case could have provided "prosecutors across Illinois with legal clarification and guidance with respect to the constitutionality and enforcement" of the statute.

Illinois' eavesdropping law is one of the harshest in the country, making audio recording of a law enforcement officer — even while on duty and in public — a felony punishable by up to 15 years in prison.

Public debate over the law had been simmering since last year. In August 2011, a Cook County jury acquitted a woman who had been charged with recording Chicago police internal affairs investigators she believed were trying to dissuade her from filing a sexual harassment complaint against a patrol officer.

Judges in Cook and Crawford counties later declared the law unconstitutional, and the McLean County state's attorney cited flaws in the law when he dropped charges in February against a man accused of recording an officer during a traffic stop.

Alvarez argued that allowing the recording of police would discourage civilians from speaking candidly to officers and could cause problems securing crime scenes or conducting sensitive investigations.

But a federal appeals panel ruled that the law "restricts far more speech than necessary to protect legitimate privacy interests."

Chicago police Superintendent Garry McCarthy has said he would favor a change allowing citizens to tape the police and vice versa.

Meanwhile, several efforts to amend the statute in Springfield have stalled in committee amid heavy lobbying from law enforcement groups in favor of the current law.

Tribune reporter Liam Ford contributed jmeisner@tribune.com