The relationship between legality and morality is summed up in the fact, that policemen have got the official name "Guardians of Peace" (in France), and not "Guardians of Justice".
Administering justice isn't a policeman's job. That's a task for a judge.
Oh, so, policemen don't arrest you for breaking the law?
Arresting you isn't administering justice. That happens later, in front of a judge.
What the policemen is doing is ending (or preventing) your breach of the peace. That's his job.
I'm a philatelist, I abuse stamps.
Y would u abuse meh