Well, most libertarian government structures call for precisely that. A police to enforce the law, a court system to provide fair rule and a small military intended for defense.
[edit: Should add that although there are certainly disputes to how to fund said services, to the best of my knowledge it's largely agreed that some court system is required.]
[edit: Should add that although there are certainly disputes to how to fund said services, to the best of my knowledge it's largely agreed that some court system is required.]