High courts such as the US Supreme Court announce legal rules that guide subsequent decisions by lower courts and other actors. Because legal rules are forward-looking in this sense, judges’ expectations about the distribution of future cases are critical. Focusing on this fact, we provide microfoundations for judicial preferences over legal rules by deriving them directly from expectations about the distribution of future cases. Doing so has important consequences: in contrast to standard assumptions in models of judicial decision-making, preferences over legal rules are asymmetric rather than symmetric. We demonstrate that this has significant implications for judicial decision-making on collegial courts. Finally, we show that changes in the case distribution—for example, as a result of technological change—can lead to significant legal change, even in the absence of ideological or doctrinal change on the court.