An extensive relationship between the Central Intelligence Agency and the New York Police Department, recently revealed by the Associated Press, might be an appropriate and effective counter-terrorism partnership. Or it might be illegal government interference in Americans' religious freedoms, an abuse of police power and a violation of laws forbidding the CIA from conducting intelligence activities on American soil.

The AP investigation suggested that cooperation between the NYPD and the CIA already had blurred legal lines, lacked sufficient oversight and flouted rules of police conduct, charges the department and the agency have denied. It's not yet clear where the truth lies.

Given the stakes, it's important to find out. Part of the formula for preventing acts of terrorism is smart, aggressive intelligence work among federal, state and local agencies. But another part of the formula requires keeping intelligence-gathering from becoming so aggressive that it does more harm than good.

Just months after the terrorist attack on the World Trade Center on Sept. 11, 2001, New York hired a controversial former CIA official, David Cohen, to overhaul the NYPD intelligence division. He brought in a CIA official, still on the CIA payroll, to redesign the city's programs.

The CIA official maintained dual offices at New York police headquarters and at the CIA's station in the city. He interviewed cops for possible positions in the new unit, taught intelligence tactics to new hires and oversaw their activities, the AP reported.

Some police officers in the new units were given undercover assignments in areas of the city that matched their own ethnicities and religious backgrounds. They began watching people and activities at Islamic mosques, ethnic bookstores, cafes and other places where New Yorkers of Middle Eastern ancestry congregated.

The unit also began enlisting confidential informants — civilians who were persuaded or pressured into secretly monitoring activities in similar areas and neighborhoods and reporting back to the cops.

In reaction to the AP story, New York police commissioner Raymond Kelly confirmed that a CIA officer is working as an intelligence adviser at the police department and supplying it with information. A CIA spokeswoman said the agency was cooperating with the NYPD but was not conducting any domestic intelligence activities.

The police department insisted that it only pursues intelligence leads and does not target people or places in New York based solely on ethnic background or religious affiliation. But some Muslim groups said that the new information about NYPD intelligence programs had damaged the force's credibility in communities it previously has relied on to help discover terrorist plans before they take shape.

History offers many cautionary tales. In the 1960s and '70s — and again in the mid 2000s — the NYPD abused its powers by targeting student and anti-war groups, as well as protesters at political conventions, without legitimate reasons to believe they were breaking any laws. The CIA's illegal domestic spying activities during the 1960s and '70s are legendary in scale and scope and were the subject of countless damning hearings.

Successful counter-terrorism does not require violating the laws and rules that protect people of all faiths and backgrounds in the United States. No one benefits if robust intelligence operations go rogue. The U.S. Justice Department should investigate the arrangement and determine which side of the line the NYPD and the CIA are on.

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