"Iíve decided to devote this post to the first issue (why the issue is hard) and Iíll follow up soon with a short second post on why non-enforcement is so attractive ... The first thing to appreciate about enforcement discretion is that huge amounts of non-enforcement are inevitable in federal criminal justice and many civil regulatory contexts. Federal criminal law is the paradigm example. Federal criminal law started out being sparse and interstitial in the early years of the Republic, but thatís no longer true. Federal criminal law today is extensive and massively punitive."