You know "Police" isn't going to be a conventional policier simply because it's directed by Maurice Pialat and Pialat doesn't do conventional. Yes, there's a 'thriller' plot involving drug dealers but the plot is secondary to the way both the police and the criminals are seen to go about their business which in many ways is much the same, (a crooked lawyer, nicely played by Richard Anconina, moves between them with seemingly consummate ease).
The central character is Gerard Depardieu's charming, brutalizing inspector who thinks nothing of beating up suspects to get a confession and both he and the film may remind you of Kirk Douglas in "Detective Story" and it's a beautiful piece of acting. Equally good, as the drug dealer's girl that Depardieu falls for, is Sophie Marceau. Ultimately the 'thriller' plot is all but jettisoned as Pialat digs deeper into the lives and backgrounds of his characters which is just as well as the plot becomes both very complicated and a little ridiculous. Still, this is a Pialat picture; mean, melancholy and fiercely intelligent.