bright-line rule

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A bright-line rule is an objective rule that resolves legal questions in a straightforward, predictable manner. Because bright-line rules determine outcome entirely based on objective factors, they best allow parties to conduct their affairs in ways that won’t result in lawsuits at the cost of a lack of flexibility when dealing with individual nuances. This lack of flexibility can lead to what many consider inequitable outcomes. 

For example, a bright-line rule in the field of auto accidents would state “In a car crash, the party whose car is damaged in the front is responsible for the accident.” Under this rule, parties who find themselves in an accident know immediately if they can recover for the damage against the other party’s insurance. Nonetheless, if the accident occurred because one party backed into the other, this bright-line rule will not accurately assign legal responsibility to the party who caused the accident. 

The primary alternative to bright-line rules are balancing tests. Balancing tests allow the court to take more factors into account than bright-line rules, but outcomes are less consistent due to the subjective nature of these additional factors. 

See, e.g. Montejo v. Louisiana, 129 S.Ct. 2079 (2009).

[Last updated in June of 2022 by the Wex Definitions Team]