That's a curious opinion and I still am too see the facts to back it up with, perhaps you can provide it. Because, as a matter of fact, I've seen exactly the opposite: laws that are not enforceable are the worst laws ever, disasterous even. If they are not "important" in their consequences, they just leave the simple folks (small businesses, for example — and hurting small business is really unwise thing to do IMO) in the state of FUD, because it takes a professional cons-man (e.g. and experienced lawyer) to know how to deal with this bullshit — it puts "honest" people in uncomfortable position, while doing nothing to people who are used to operating in perpetual state of moral hazard, which means it is beneficial to people who are most likely to exploit the law (or its absence) to start with. If this law is more "important" and involves a lot of regulations it fuels corruption, because, again, it's beneficial for dishonest people — it's up to somebody's opinion if you are breaking the law, and opinions can be swayed with some money…
In the most general and seemingly "harmless" case these laws do exactly nothing: nobody is following them and nobody tries to punish people for not following them. This just makes the legal system more complicated (and — yes, there are plenty of such laws, and this is one of the reasons so many legal systems are shit) and provokes the disrespectful, hand-waving attitude towards the law, which isn't a good thing either.