Opinion of the Court
(quoting Perrin v. United States, 444 U. S. 37, 42 (1979)). See also Sandifer v. United States Steel Corp., 571 U. S. 220, 227 (2014). After all, if judges could freely invest old statutory terms with new meanings, we would risk amending legislation outside the “single, finely wrought and exhaustively considered, procedure” the Constitution commands. INS v. Chadha, 462 U. S. 919, 951 (1983). We would risk, too, upsetting reliance interests in the settled meaning of a statute. Cf. 2B N. Singer & J. Singer, Sutherland on Statutes and Statutory Construction §56A:3 (rev. 7th ed. 2012). Of course, statutes may sometimes refer to an external source of law and fairly warn readers that they must abide that external source of law, later amendments and modifications included. Id., §51:8 (discussing the reference canon). But nothing like that exists here. Nor has anyone suggested any other appropriate reason that might allow us to depart from the original meaning of the statute at hand.
That, we think, holds the key to the case. To many lawyerly ears today, the term “contracts of employment” might call to mind only agreements between employers and employees (or what the common law sometimes called masters and servants). Suggestively, at least one recently published law dictionary defines the word “employment” to mean “the relationship between master and servant.” Black’s Law Dictionary 641 (10th ed. 2014). But this modern intuition isn’t easily squared with evidence of the term’s meaning at the time of the Act’s adoption in 1925. At that time, a “contract of employment” usually meant nothing more than an agreement to perform work. As a result, most people then would have understood §1 to exclude not only agreements between employers and employees but also agreements that require independent contractors to perform work.
What’s the evidence to support this conclusion? It turns out that in 1925 the term “contract of employment” wasn’t defined in any of the (many) popular or legal dictionaries
