MT HB791

Redefines public nuisance as conditions arising from real property use that unlawfully interfere with public rights, and explicitly excludes from public nuisance claims: lawful activities, government-authorized actions, shooting range noises, product design/manufacturing/marketing, firearms and ammunition, and aggregation of individual injuries

Abrogates common law of public and private nuisance in Montana, replacing it entirely with statutory definitions and requirements that apply to causes of action accruing on or after October 1, 2025

Limits government remedies in public nuisance actions to criminal prosecution, injunctive relief, and quantifiable abatement costs proven by clear and convincing evidence; prohibits recovery of damages or costs of abating potential future nuisances

Requires private persons bringing public nuisance claims to demonstrate a "special injury" different in kind from injuries to the general public, proven by clear and convincing evidence, with remedies limited to compensatory damages only; prohibits class actions for public nuisance

Exempts opioid-related litigation filed by the Montana Department of Justice within 4 years of October 1, 2025, and protects agricultural/farming operations from nuisance claims when they predate complaining residents or businesses