Law Matters—Less Than We Thought.

This article reports on a pre-registered 2×2×2 factorial randomized lab experiment involving 61 federal judges to assess whether legal rules influence judicial decisions, whether rules constrain more than standards, and whether legally irrelevant sympathies affect outcomes. Judges decided a realistic fictitious auto accident case with varying forum (Wyoming or South Dakota), accident location/common domicile (Kansas or Nebraska), and sympathy toward plaintiff or defendant. The study found only weak evidence that law influences decisions, with judges following clear legal rules (lex loci delicti) about 77% of the time under a rule-based forum (Wyoming) and less than 50% under a standard-based forum (South Dakota), and no evidence that sympathy affected rulings. The experiment’s design manipulated intra-U.S. geographic elements to induce legal variation realistically, but results suggest judges often deviated from legal directives, sometimes avoiding damage caps or favoring traditional choice-of-law rules regardless of the applicable standard. These findings align with prior research indicating limited internal force of law in judicial decision-making absent external enforcement mechanisms like appeals or public scrutiny.