The details were out of a different era, even a different country: undercover agents eavesdropping at lunch counters, informants in every mosque, the license plates of worshippers recorded. One NYPD report noted that "Muslim prayer mats are hanging on the wall at an Indian restaurant."

This was America of the post-9/11 era, where safety was most salient. Starting in 2003 the New York Police Department tried to map Muslim communities in and around the city in the name of national security, establishing surveillance solely on the basis of religion. A lawsuit against the surveillance filed by a group of Muslim individuals, organizations and businesses was dismissed in February, but last week a federal appeals court reversed that decision. The plaintiffs will have another day in court.

The NYPD program, known as the "demographics unit," was discontinued by Police Commissioner Bill Bratton in 2014. But the lawsuit has larger implications on the national stage, shedding light on the efficacy and legitimacy of domestic surveillance policies in the era of the Patriot Act. It gives plaintiffs standing to challenge programs like this one by demonstrating harm on the basis of unequal treatment because of religion.

In a strongly worded opinion, Judge Thomas L. Ambro wrote of this kind of surveillance, "We have been down similar roads before. Jewish-Americans during the Red Scare, African-Americans during the Civil Rights Movement, and Japanese-Americans during World War II are examples that readily spring to mind."

This historical perspective is vital. Terrorism is not the only threat the nation has faced. It is irresponsible to claim that this threat demands an entirely new response -- a harsher, more punitive one -- in the name of public safety. Focused investigations that target terrorist activity should be a prime objective for police and national law enforcement agencies. But blanket surveillance of entire communities alienates U.S. citizens and gives fuel to our detractors -- not to mention being against the American principles of equality that we brandish and cherish most dearly in troubled times.