The written law is binding, but the unwritten law is much more so. You may break the written law at a pinch and on the sly if you can, but the unwritten law — which often comprises the written — must not be broken. Not being written, it is not always easy to know what it is, but this has got to be done.

The Law - The Note-Books of Samuel Butler (1912) - Part VII - On the Making of Music, Pictures, and Books