...this Court's precedents. Since such an interpretation is agency action, not a
post
hoc rationalization of it, and assumes a form expressly provided for by Congress when embodied...interpretation of OSH Act regulations in an administrative adjudication, however, is agency action, not a post hoc rationalization of it. Moreover, when embodied in a citation, the Secretary's...necessarily appear in forms undeserving of judicial deference. Our decisions indicate that agency "litigating positions" are not entitled to deference when they are merely appellate counsel's " post hoc...