It is an unavoidable fact of contemporary American life that we are being watched. Whether by government spycraft, consumer data hoarding, or networked surveillance cameras, a citizen in this era is subject to observation, with scant protection against it.

It's been a slightly different story for cops. Municipal police departments around the country, in states including Illinois, Florida, Maryland, and New Hampshire, have been able to go unwatched. More precisely, they have been able to arrest individuals for the mere fact of filming police activity in public. Under the pretext of protecting official business from public glare, cops across the US have carried out all manner of brutalities — from harassment, to beatings, to sodomizing detainees stopped for mere traffic violations, to murder — with impunity, safe in the assumption that any recordings of their actions are in their own hands.

A federal court this week, however, ruled that cops can no longer maintain a monopoly over recording arrests and police action. Filming cops, the court ruled, is protected by the First Amendment. The ruling, which is only binding in the four states in the First Circuit District (Maine, Massachusetts, New Hampshire and Rhode Island) and in Puerto Rico, resulted from a case brought by a New Hampshire woman arrested for filming police carrying out a traffic stop. The case is now being returned to a lower court for trial.

"It is clearly established in this circuit that police officers cannot, consistent with the Constitution, prosecute citizens for violating wiretapping laws when they peacefully record a police officer performing his or her official duties in a public area," the First Circuit appeals court ruled.

The decision is a small victory in the fight against police brutality. It establishes as constitutionally protected the sort of activity that activists under the banner CopWatch have been carrying out in communities plagued by police harassment for years. CopWatch recordings have played an important role in revealing how cops regularly offer skewed or utterly false narratives when making violent arrests or, for example, shooting unarmed black teens.

To be sure, the assured ability to film cops does not spell the end of police violence nor their impunity. If filming cops were enough, there wouldn't be so many officers proven to have been abusive without criminal records and still serving on police forces around the country.

The NYPD officer who shot and killed unarmed Bronx teen Ramarley Graham in his grandmother's bathroom, then lied and claimed the 18-year-old had been carrying a gun, was found not guilty of manslaughter. Three officers who, in 2008, arrested Michael Mineo, pinned him down, pulled down his trousers and sodomized him with a baton were also found not guilty of the minimal charges they faced of hindering prosecution and official misconduct. The Fullerton, California cops who beat homeless and schizophrenic Kelly Thomas to death as he cried out for his dad walked free, despite graphic surveillance camera video of the fatal assault. The BART officer who shot Oscar Grant (again, unarmed) at point blank range as he lay on a train station platform spent less than a year in prison, though cell phone video of the execution was seen by millions.

That the Oakland cop, Johannes Mehserle, was prosecuted and convicted at all for killing Grant is perhaps evidence of the importance of filming cops. But the justice system's lenient treatment of Grant's killer, Graham's killer, Mineo's abusers, and many many more vicious cop actions sends a clear message that police brutality remains state-sanctioned. Filming cops is crucial, but borrowing from that well-loved anti-police protest chant: it's no justice, and it's no peace.

Follow Natasha Lennard on Twitter: @natashalennard