Police Departments are concerned with public policy, not public law.
They are code enforcers, revenuers.
They aren't even agencies of government.
They are a standing Army on American soil. Now being Federalized.
Otherwise why all the police atrocities at public outcries protests and the like.
"... [Of] all the contrivances for cheating the laboring classes of mankind, none has been more effective than that which deludes them with paper money."
~ Daniel Webster