"The job of law enforcement is to prevent crime, to detain criminal suspects and to gather evidence."

Unfortunately, the job of law enforcement is in fact to enforce the law. The same law which is written by people you don't know and are not asked your opinion on. The same law which is influenced by people richer and more connected than you. A government consists of a group of people who threaten other people with violence (through the police) when they do not agree with their actions. The only way to have real justice is to not have a police force, or a government, for that matter.