Slate has begun a series on U.S. laws that aren’t observed or enforced:
The importance of understanding why and when we will tolerate lawbreaking cannot be overstated. Lawyers and journalists spend most of their time watching the president, Congress, and the courts as they make law. But tolerance of lawbreaking constitutes one of the nation’s other major—yet most poorly understood—ways of creating social and legal policy. Almost as much as the laws that we enact, the lawbreaking to which we shut our eyes reflects how tolerant U.S. society really is to individual or group difference. It forms a major part of our understanding of how the nation deals with what was once called “vice.” While messy, strange, hypocritical, and in a sense dishonest, widespread tolerance of lawbreaking forms a critical part of the U.S. legal system as it functions.
Start reading here: American Lawbreaking