Enforcement Discretion: Thinking about the Executive, the Rule of Law and the Separation of Powers

The topic of enforcement discretion is the subject of an interesting series of posts by Zachary Price over at the Volokh Conspiracy. The impetus for Price's series and his underlying article ("Enforcement Discretion and Executive Duty") comes from several recent American episodes, such as President Obama's decision not to enforce certain provisions of the Affordable Care Act (see e.g. here), the policy not to pursue certain breaches of federal drug laws and the policy not to seek minimum sentences for some drug offences.

At first blush, this looks much like the dispensing power that common law jurisdictions dispensed with many centuries ago. Price argues, however, that there are constitutional provisions that give the American executive discretion to refuse to enforce laws on a case-by-case basis though not as a matter of general policy. My interest is less in the specifics of U.S. constitutional law than in the generalities of enforcement discretion.