The article "The Myth of the Rule of Law"[1] has been linked a few times on HN, and I think it sums up this idea pretty well. It basically says that in many (most?) cases the law is subject to interpretation that depends on the politics of the interpreter (be they a lawyer, judge or member of a jury). The "letter of the law" isn't nearly as simple as people believe, ambiguity is the name of the game.

1: http://faculty.msb.edu/hasnasj/GTWebSite/MythWeb.htm