arm. Mfrs. v. FTC, 637 F.2d 877, 880 (2d Cir. 1981) (‘this generous construction of agency rulemaking authority has become firmly entrenched”); Nat’! Petroleum Refiners Ass’n v. FTC, 482 F.2d 672, 686 (D.C. Cir. 1973) (“plain, expansive language” of the rulemaking grant at issue, together with the “‘broad, undisputed polic