The area in which Southfork subdivision is located is classified as "Open Range". Owing to Colorado's ranching heritage, land classified as Open Range is subject to what is referred to as "Fence Law". (Colorado Revised Statutes Title 35 Article 46)

Under Colorado's fencing laws, the property owner has the option to fence, or not to fence their property. If the property is not fenced, the owner of any trespassing livestock is not liable for damage done to the property by the livestock. If the property is protected by a "lawful fence" (any fence that could reasonably be expected to prevent the passage of horses or cattle), the owner of any trespassing livestock is liable for damage done to the property by the livestock.

What this means:

Livestock owners whose livestock wanders onto property not protected by a "lawful fence" are not subject to criminal or civil penalties for property damage done by the livestock.

What this DOES NOT mean:

MYTH : Because it's Open Range, you can go where ever you want if there is no fence.
FACT : People ARE NOT livestock (at least we have not reached the "soylent green" point yet, thank goodness). While livestock can not be reasonably expected to understand the concept of trespassing, people can. Any person who unlawfully enters another's property (enters without express or implied permission of the property owner) can be prosecuted under Colorado law. It does not matter if you happen to be riding a horse (or any other livestock) at the time; entering without permission is trespassing. Period. Colorado law also does not require that property be fenced or posted as private property. The simple version: Unless you KNOW it is publicly accessible property, DON'T GO THERE.

MYTH : Because it's Open Range, you do not have to restrain dogs and other pets.
FACT : Dogs and other household pets ARE NOT livestock. In the fence law, livestock in Colorado is defined as: Horses, cattle, mules, asses, goats, sheep, swine, buffalo, and cattalo (cross breed of bison and cattle). Pet owners are subject to civil and criminal liability for all damage or injury caused by animals they own that commit such damage or injury while trespassing on another's property or while on public property. If pets have not been properly inoculated and are permitted to run at large, the owner is subject to fines or imprisonment.

MYTH : Because it's Open Range, livestock owners may let livestock animals roam anywhere.
FACT : Livestock owners must provide ample pasture, forage and water for the livestock on their property. If ample pasture, forage or water are not provided, livestock owners are liable for any damage done by livestock attempting to obtain these, regardless of whether or not the damaged property was fenced. Livestock owners are only shielded from penalties for property damage under fence law; if trespassing livestock cause personal injury to others, the livestock owner is responsible. Livestock owners are required to control access of livestock to public roadways. Livestock owners are responsible for any property damage or personal injury done by their livestock on any public roadway.