I've thought along similar lines, but with a slightly different intent: to refactor existing sets of law. I started off thinking about trying to improve & streamline the law, but eventually realized there might actually be a market as a analytical tool for lobbyists. In any case, trying to build a useful constraint system or search engine, etc. out of human-muddled laws sounds very messy and fun from a programmer's point of view. The actual legal aspects might be intractable, but I'll leave the naysaying to the lawyers. :)