Opinion of the Court
Orthopedic Associates, P. A. v. Allstate Ins. Co., 559 U. S. 393, 419–420 (2010) (Stevens, J., concurring in part and concurring in judgment). Many rules “are rationally capable of classification as either.” Hanna v. Plumer, 380 U. S. 460, 472 (1965); see also Sun Oil Co. v. Wortman, 486 U. S. 717, 726 (1988) (“Except at the extremes, the terms ‘substance’ and ‘procedure’ precisely describe very little except a dichotomy.”). Procedure, after all, is often used as a vehicle to achieve substantive ends. When a governor vetoes a bill because of a disagreement with its policy consequences, has the governor exercised a procedural or substantive restraint on lawmaking? Smiley did not endorse such murky inquiries into the nature of constitutional restraints, and we see no neat distinction today.
D
Were there any doubt, historical practice confirms that state legislatures remain bound by state constitutional restraints when exercising authority under the Elections Clause. We have long looked to “settled and established practice” to interpret the Constitution. The Pocket Veto Case, 279 U. S. 655, 689 (1929). And we have found historical practice particularly pertinent when it comes to the Elections and Electors Clauses. Smiley, 285 U. S., at 369 (Elections Clause); Chiafalo v. Washington, 591 U. S. ___, ___–___ (2020) (slip op., at 12–14) (Electors Clause).
Two state constitutional provisions adopted shortly after the founding offer the strongest evidence. Delaware’s 1792 Constitution provided that the State’s congressional representatives “shall be voted for at the same places where representatives in the State legislature are voted for, and in the same manner.” Art. VIII, §2. Even though the Elections Clause stated that the “Places” and “Manner” of federal elections shall be “prescribed” by the state legislatures, the Delaware Constitution expressly enacted rules govern-
