I have just done this little article as I think that there is often confusion between rules and customs;
http://thenakedapegetsdressed.blogspot.com/
Laws- written -enforceable- some sanctions= you must not appear naked in public with some exceptions
Rules - enforceable - You may not come in or you must leave
Rules - unclear-such as smart dress required
Custom- written / unwritten / clear/unclear/ able to be known/unable to be known
Codes-......