Supreme Court judgments based on reasons outside the law are unlikely to harm its legitimacy.

While almost all judgments from the Supreme Court are based on some kind of existing law, there are a small number which are not. Instead justices use public opinion, religious texts, and their own personal beliefs to justify their decisions. In new research, Chris Bonneau, Jarrod Kelly, Kira Pronin, Shane Redman and Matt Zarit examine whether such ‘extralegal’ decisions harm the Court’s legitimacy in the eyes of the public. They find that when moral or public opinion reasons are provided in addition to legal precedents, then public opinion about that decision’s legitimacy does not change. Members of the public only change their opinion on a decision’s legitimacy when they believe one specific reason is inappropriate and they disagree with the outcome.