Nobody ever comes to the park I go to without their tags. Maybe that is because we have to register every year to get access. If the pups are not utd on all their shots including rabies they do not get access the next year. Not completely effective, but it does give some piece of mind to know the dogs are all current on shots, and healthy. They also have a no heat policy, and I never have seen one in the park, but it may happen for all I know.