On June 2, 2009, a janitor in an office building in New Brunswick, N.J., noticed what he thought was terrorist-related literature and sophisticated surveillance equipment in an office he had been assigned to clean. He told his boss, who called the local police, who notified the FBI. Later in the day, the FBI and the New Brunswick police broke into the office and discovered five men busily operating the equipment. Four of the men were police officers from the New York City Police Department (NYPD), and the fifth was a CIA agent.

The conundrum faced by all of these public servants soon became apparent. Who should arrest whom?

Should the FBI agents and the local cops arrest the NYPD and the CIA agent for violating the U.S. and New Jersey constitutions, both of which prohibit searches and seizures without search warrants, and for violating federal and New Jersey laws against wiretapping and surveillance? Should the NYPD and the CIA agent arrest the FBI agents and the local cops for breaking and entering and obstructing a governmental function without a search warrant? Did the FBI and the local cops even have a search warrant? Was the NYPD/CIA surveillance a lawful governmental function?

No one at the scene of this unique encounter was arrested. In return for not becoming a defendant, everyone agreed not to become a complainant. The FBI and the New Brunswick police went home, and the NYPD cops and their CIA mentor went back to their surveillance—even though everyone in that office had sworn the same oath to uphold the U.S. Constitution and the laws written pursuant to it.

Among those laws are the state statutes that limit the authority and jurisdiction of local cops to the municipality that employs them, and the federal statutes that limit the legal ability of CIA agents to steal secrets only from foreigners outside the U.S. Stated differently, the NYPD has no authority or jurisdiction to engage in surveillance in New Jersey, and the CIA has no authority or jurisdiction to engage in surveillance in the U.S.

Nevertheless, we now know from the candid admissions last week of NYPD Commissioner Raymond Kelly that the NYPD has been spying without search warrants on Muslim groups in New Jersey and elsewhere for 10 years. Former New Jersey acting governor and current state Sen. Richard Codey recalls authorizing the NYPD—and not the CIA—to inspect railroads and ferries that travel back and forth between New Jersey and New York in 2005. He says he never authorized surveillance. No public official in New Jersey has come forward to acknowledge awareness of all this, and Kelly says the spying will continue. But he needs a search warrant.

Can the police spy on us? Only if they have probable cause to believe that criminal behavior is taking place and a search warrant signed by a judge. Short of probable cause about the very persons on whom they are spying, not about a group to which those persons belong by birth or by choice, the police may not lawfully spy, and judges will not sign search warrants without specific probable cause about specific persons. The specificity is required by the language of the Fourth Amendment. That language also guarantees that quintessentially American right—the right to be left alone—by establishing articulable suspicion as the linchpin of all police pursuit of anyone for anything, and probable cause as the trigger for search warrants.

Can the police choose a target upon whom to spy based on the target's religion? No. The courts have been clear that under no circumstances may religion lawfully be the sole or even the principal basis for surveillance. That's how World War II got started: German police targeted Jews because they were Jews, and for no legitimate law enforcement purpose and without probable cause.

Was the New Brunswick operation criminal? Yes, it was. It's not too late to charge the NYPD officers or the CIA agent in state or federal court for spying. It's also not too late to charge the FBI agents and the New Brunswick cops in state or federal court for failing to obtain a search warrant (if they didn't have one), and for malfeasance in office by not arresting the spies.

The sacrifice of liberty for safety is illusory. The liberty lost does not return. The safety gained is not real. Who in New Jersey voluntarily gave up his liberty? Who can feel safe or free with government agents secretly and unlawfully monitoring them? What is the reliability and vitality of constitutional guarantees if those in whose hands we repose them actively violate them? What religious group might law enforcement target next? How dangerous to personal freedom is a cabal of law enforcement when it looks the other way to avoid prosecuting its own?