I was reading this passage from Scalia’s opinion in Talk America, Inc. v. Michigan Bell Telephone Co., and thought to myself, this sounds like Montesquieu. Then I got to the end of the sentence, and realized it was Montesquieu!

When Congress enacts animprecise statute that it commits to the implementation of an executive agency, it has no control over that implementation (except, of course, through further, more precise, legislation). The legislative and executive functions are not combined. But when an agency promulgates an imprecise rule, it leaves to itself the implementation of that rule, and thus the initial determination of the rule’s meaning. And though the adoption of a rule is an exercise of the executive rather than the legislative power, a properly adopted rule has fully the effect of law. It seems contraryto fundamental principles of separation of powers to permit the person who promulgates a law to interpret it aswell. “When the legislative and executive powers are united in the same person, or in the same body of magistrates, there can be no liberty; because apprehensions may arise, lest the same monarch or senate should enact tyrannical laws, to execute them in a tyrannical manner.” Montesquieu, Spirit of the Laws bk. XI, ch. 6, pp. 151–152(O. Piest ed., T. Nugent transl. 1949).