Amoral, very violent, using any means to gain an end, the cops in 'La Balance' make 'The Sweeney' look like pekingese puppies. But when a film has no character to sympathise with, when you don't care what happens to any of them, then it just becomes uninvolving. The story might pass the time, but that's about it. There is a relatively innocent pimp and his girl who get trapped between the cops and the bad guys, but there is no attempt to make them three-dimensional - they are there because the plot demands it.
Some compensation is found in the well-caught imagery and atmosphere of Belleville, and there is a good scene involving a shoot-out in a traffic jam.
Nathalie Baye, fresh from 'The Return of Martin Guerre', gets top-billing, and does O.K., nothing more. Much the same can be said of Philippe Leotard. Richard Berry, thirty-odd years before his role as a very different cop, 'Lanester', (catch it on Walter Presents - recommended) , is given nothing to work with and so too becomes a cipher.
In sum, it's too brash.