And wikipedia actually has a pretty good entry/overview on the history of law enforcement and policing. Everywhere there humans, for as long as there have been humans, there has been crime and conflict and most societies and cultures have had some way, for better or worse, to deal with it and to try to maintain order. How any culture deals with crime and conflict and disagreements between it’s members depends a lot on the culture and it’s values, the size of the population and what type of issues are more typical to that society or culture. A society consisting of a relatively small population dispersed among villages is going to have a different system and different “policing” institutions than a larger, more densely populated urban area.
And this site, the book World Encyclopedia of Police Forces and Correctional Systems has some information. You can’t get full access to the text without registering, but they do offer a 3 day free trial. The chapter The Future of Public Safety offers at least someone’s view of two possible approaches to law and order and policing in the future.