Paper by Cass Sunstein and Adrian Vermeule: “Administrative agencies frequently say “not now.” They defer decisions about rulemaking or adjudication, or decide not to decide. When is it lawful for them to do so? A substantial degree of agency autonomy is guaranteed by a recognition of resource constraints, which require agencies to set priorities, often with reference to their independent assessments of the relative importance of legislative policies. Unless a fair reading of congressional instructions suggests otherwise, agencies may also defer decisions because of their own policy judgments about appropriate timing. At the same time, agencies may not defer decisions, or decide not to decide, if Congress has imposed a statutory deadline, or if their failure to act amounts to a circumvention of express or implied statutory requirements, or amounts to an abdication of the agency’s basic responsibility to promote and enforce policies established by Congress.”