The problem of changed circumstances recurs throughout constitutional law. Statutes often outlive the conditions they were meant to address. A once-reasonable law may come to impose burdens that the legislature never intended and would not now be willing to impose. This Note asks whether courts are ever permitted to step in and declare that, as a result of postenactment changed circumstances, a once-valid law can no longer be constitutionally applied. It argues that the propriety of changed circumstances review depends first on whether the applicable doctrinal test is substantive or motives-based. A substantive test is one that imposes an absolute prohibition on certain categories of legislation, or requires a particular degree of fit between legislative means and ends. A motives-based test asks only whether the enacting legislature intended to further an impermissible objective. This Note demonstrates that where the underlying test is substantive, a reviewing court must at least consider whether circumstances have sufficiently changed since the challenged law’s enactment to justify striking it down. If the test is motives-based, then the court should generally consider only whether the statute is valid based on facts as they existed when it first went into effect.