Thornton, CO Animal Ordinances: Breed Restrictions (2026)

Section 6-17(a) makes it unlawful to possess an animal that inflicts a puncture wound or abrasion not rising to bodily injury, that without provocation repeatedly snaps, lunges, or approaches a person while growling or snarling in a threatening manner, that chases or runs at a person while snapping, biting, growling, or snarling, or that harasses passersby by leaning on or over fences while snarling or growling. Section 6-17(b) creates defenses, so an animal is not deemed aggressive if the threatened person was trespassing, was in the owner's vehicle unlawfully, was attacking another person, was breaking up an animal fight, or deliberately provoked the animal.

Once an owner is cited under Section 6-17(a)(1), impoundment is mandatory if the animal has a prior animal-attack conviction; otherwise, impoundment under Section 6-18 is discretionary pending a fact-finding dispositional hearing under Section 6-19, held within ten days, where the court weighs the animal's conduct, prior violations, and any corrective steps the owner has taken. 00, up to a year in jail, and mandatory spay/neuter and microchipping, and the court may additionally bar extension leashes, require a fixed leash no longer than four feet, order muzzling off the owner's property, mandate behavior training, or require a warning sign on the property.