In the unenforceable, that's the case where there actually is legislation or what Moulton calls law. But otherwise, it's well understood New York that even if J. Walking is illegal, it's not enforced. And molten gives a great example that made me think of Twitter or the US House of Representatives right now. It's much more efficient if we can use discretion instead of a rule.
Civilization and the pleasantness of everyday life depend on unwritten rules. Early in the 20th century, an English mathematician and government official, Lord Moulton, described complying with these rules as "obedience to the unenforceable"--the area of personal choice that falls between illegal acts and complete freedom. Listen as economist Michael Munger talks with EconTalk's Russ Roberts about the power and challenge of the unenforceable.