The Political Economy of Policing
Further reading:
For a New Liberty: The Libertarian Manifesto by Murray N. Rothbard (Chapter 12)
The Enterprise of Law: Justice Without the State by Bruce L. Benson
To Serve and Protect: Privatization and Community in Criminal Justice by Bruce L. Benson
The Voluntary City: Choice, Community, and Civil Society edited by David T. Beito, Peter Gordon & Alexander T. Tabarrok (Chapters 6-7)