Let Sleeping Cops Lie (1988)

Original title: Ne réveillez pas un flic qui dort

This movie tells the story of a group of right-wing cops have begun carrying out vigilante justice on drug dealers and other crime figures who might otherwise avoid punishment for their misdeeds. Police inspector Grindel (Delon) understands the feelings which motivate these deeds, but does not approve. However, he is not highly motivated to put an end to the group's activities until it begins to appear that they are now attacking fellow cops for reasons which are unclear.