You found a dog (or cat) wandering around the streets of Boulder, Colorado. You took him/her into your home in Boulder and gave her/him food and water. Maybe you even cleaned some wounds, or brushed his/her coat or teeth, clipped some toenails, etc. You took care of the dog, you fell in love, and the dog's person is nowhere to be found.
So what do you do? Is the dog now yours?
Not quite! In Colorado, the law on abandoned property says that the property cannot legally be yours (is not legally considered abandoned) until five (5) years from the date the property was lost or abandoned.
Of course, 5 years is a long time in the life of an animal! So, the best thing to do is to post flyers around the area where you found the dog, post online in your area (nextdoor.com, facebook.com, etc.) and see if anyone contacts you. The more you can show you tried to find the original owner, the more likely the court is to see the animal as "abandoned" if the original owner sues you for the pet, later.
There's no specific statute or law that addresses animals found by people who are not their owners, which is unfortunate because it happens pretty frequently. Unfortunately, a vet trip 3 or 4 years later could result in a long-lost microchip being found and the original owner gets contacted. It is a long, contentious, and heart-wrenching battle for ownership of the pet.
If you and the original owner live close enough and can come to an agreement, it might be possible to share custody of the dog, or buy out the other person.
Call an experienced Colorado animal attorney at 303-623-4000 who will handle your case with the compassion it deserves.