It was originally conceived to have a much less heavy-handed scope though, but has been strengthened over time to something near-impossible to thwart.
When the prosecutors refuse to bring charges against police, the only remedy is civil court, which QI forbids in most cases. There are exceptions, but there should be more.
Having said that, nothing prevents you from suing the police department, city or government. It's just that the people who commit these acts have no repercussions because the prosecutors don't bring charges and their superiors support that type of activity.
I can't overstate how dangerous and what a powder keg this is right now. If we ever had a hot civil war, I suspect it would be citizens vs police, not liberal vs conservative.