And yet I've never seen that phrase used other than when cops are defending their colleague who is on video murdering/raping/beating someone innocent, or by those calling for reform who are criticizing the cops covering for each other's crimes.
Even I have seen it used in other senses by Americans, and I've never been to America. AFAICT it has only acquired that sense, at least to the extent it currently has, after #BLM. Might be an age thing, that most of your cultural impressions are of a more recent date than the majority of mine? (And, say, Ted T'so's.)
And it's in a context where some group of people with special power is acting in bad faith to avoid having to follow the rules, and setting up "us vs them" arguments to do so!
