I appreciate where you’re coming from but your argument is just too abstract. As far as the letter of the law, the police are probably more limited than ever. This is certainly true in this particular case where prior to 1985 a cop could shoot any fleeing felon.
A lot of police work happens at the gut level. You can pile on the formal limits but ultimately it’s cultural conditioning that shapes how a policeman relates to the public he serves.
Is this written down anywhere, or are you just promoting your gut-level sense of a "rule of thumb" from before the onset of the Golden Age of The Police State?
We'll also have to note that Walter Scott was NOT a felon.
And just because Slager assaulted Scott in the back alley doesn't make Scott a felon.
It's more like it makes Slager a vigilante.