A funny thing happened in New York City last week: Cops stopped arresting people. Not altogether, of course—that would be anarchy. But since last Monday, the number of arrests in America's largest city plummeted by two-thirds compared to the previous year. The decline is a conscious slowdown by New York's police force to protest City Hall's perceived lack of support for law enforcement.

NYPD officers and union leaders have been at odds with Mayor Bill de Blasio in the wake of the Eric Garner case and the killings of Officers Wenjian Liu and Rafael Ramos this month. In their latest move, officers have begun a "virtual work stoppage" throughout the city by making fewer low-level arrests and issuing fewer citations. The Patrolmen's Benevolent Association, New York's largest police union, urged its members not to make arrests "unless absolutely necessary," according to the New York Post's report.

[The slowdown] has helped contribute to a nose dive in low-level policing, with overall arrests down 66 percent for the week starting Dec. 22 compared with the same period in 2013, stats show.

Citations for traffic violations fell by 94 percent, from 10,069 to 587, during that time frame.

Summonses for low-level offenses like public drinking and urination also plunged 94 percent—from 4,831 to 300.

Even parking violations are way down, dropping by 92 percent, from 14,699 to 1,241.

Drug arrests by cops assigned to the NYPD’s Organized Crime Control Bureau—which are part of the overall number—dropped by 84 percent, from 382 to 63.

Although safety is cited as the reason for the police union's move, political considerations are central. "This is not a slowdown for slowdown’s sake," a police source told the Post. "Cops are concerned, after the reaction from City Hall on the Garner case, about de Blasio not backing them." The NYPD slowdown also comes amid protracted contract negotiations between police unions and the mayor's office.

The Post, which enthusiastically championed the NYPD during this year's turmoil, portrayed this slowdown in near-apocalyptic terms—an early headline for the article above even read "Crime wave engulfs New York following execution of cops." But the police union's phrasing—officers shouldn't make arrests "unless absolutely necessary"—begs the question: How many unnecessary arrests was the NYPD making before now?

Policing quality doesn't necessarily increase with policing quantity, as New York's experience with stop-and-frisk demonstrated. Former Mayor Michael Bloomberg asserted that the controversial tactic of warrantless street searches "keeps New York City safe." De Blasio ended the program soon after succeeding him, citing its discriminatory impact on black and Hispanic residents. Stop-and-frisk incidents plunged from 685,724 stops in 2011 to just 38,456 in the first three-quarters of 2014 as a result. If stop-and-frisk had caused the ongoing decline in New York's crime rate, its near-absence would logically halt or even reverse that trend. But the city seems to be doing just fine without it: Crime rates are currently at two-decade lows, with homicide down 7 percent and robberies down 14 percent since 2013.

The slowdown also challenges the fundamental tenets of broken-windows policing, a controversial strategy championed by NYPD Commissioner Bill Bratton. According to the theory, which first came to prominence in a 1982 article in The Atlantic, "quality-of-life" crimes like vandalism and vagrancy help normalize criminal behavior in neighborhoods and precede more violent offenses. Tackling these low-level offenses therefore helps prevent future ones. The theory's critics dispute its effectiveness and contend that broken-windows policing simply criminalizes the young, the poor, and the homeless.

Public drinking and urination may be unseemly, but they're hardly threats to life, liberty, or public order. (The Post also noted a decline in drug arrests, but their comparison of 2013 and 2014 rates is misleading. The mayor's office announced in November that police would stop making arrests for low-level marijuana possession and issue tickets instead. Even before the slowdown began, marijuana-related arrests had declined by 61 percent.) If the NYPD can safely cut arrests by two-thirds, why haven't they done it before?

The human implications of this question are immense. Fewer arrests for minor crimes logically means fewer people behind bars for minor crimes. Poorer would-be defendants benefit the most; three-quarters of those sitting in New York jails are only there because they can't afford bail. Fewer New Yorkers will also be sent to Rikers Island, where endemic brutality against inmates has led to resignations, arrests, and an imminent federal civil-rights intervention over the past six months. A brush with the American criminal-justice system can be toxic for someone's socioeconomic and physical health.

The NYPD might benefit from fewer unnecessary arrests, too. Tensions between the mayor and the police unions originally intensified after a grand jury failed to indict a NYPD officer for the chokehold death of Eric Garner during an arrest earlier this year. Garner's arrest wasn't for murder or arson or bank robbery, but on suspicion of selling untaxed cigarettes—hardly the most serious of crimes. Maybe the NYPD's new "absolutely necessary" standard for arrests would have produced a less tragic outcome for Garner then. Maybe it will for future Eric Garners too.