into the residual category, under which a court gives Skidmore deference to an agency's informed position: As a practical matter, an agency operates under the agency's interpretative rules. The law permits parties before the agency to argue alternative interpretations, and under the law, agencies are supposed to respond to the arguments, and not foreclose alternatives suggested by parties. But as a practical matter, agencies seldom give anything more than short shrift consideration to alternatives. On judicial review, the practical reality is that a court is most likely to agree with the agency, under Skidmore deference. But Skidmore deference is only as strong as the quality of the agency's analysis, and courts regularly overturn "interpretative" rules. Chevron/Auer: Formal interpretations of statutes or regulations Some agency interpretations are binding on parties and the courts, under Chevron deference: But an agency has to earn this deference; it is far from automatic. When an agency interprets its own organic statute (for Chevron) or a regulation that it promulgated (under Auer), and the interpretation meets all the following prerequisites, only then does the agency receive the high deference of Chevron or Auer. Under "Chevron step zero", an agency only receives deference when interpreting a statute or rule within its delegated authority, and that it is charged with administering. Under "Chevron/Auer step one", an agency only earns high Chevron/Auer deference for an interpretation where there is an ambiguity in words in the statute or rule, or a delegation of authority by Congress to fill gaps. Under "Chevron/Auer step two", an agency interpretation only receives deference if it is a "reasonable" interpretation of the statutory language considered with statements of Congressional intent, and is supported by a reasonable explanation. In addition to the three classical steps, an agency must observe additional procedural formalities: Not every silence is a Chevron/Auer "gap": the agency must be charged with filling the gap. Silences without a Congressional rulemaking charge are just silences, leaving the underlying default in place. The interpretation or implementing regulation at issue must tend to resolve the precise ambiguity or fill the precise gap: overly imprecise rules or interpretations do not receive Chevron or Auer deference. High Chevron/Auer deference requires that the agency publish its interpretation with some degree of formality, including any procedural formalities that Congress specifies, either for agencies in general (such as the Paperwork Reduction Act), or specific to the agency—while full-blown notice and comment