Legally, a vet is allowed to euthanize any dog as long as they have the owner's permission. What may stop a vet from euthanizing a dog is their own moral dilemma. Many vets refuse to perform what is known as “convenience euthanasia.” Veterinarians are happy enough to perform euthanasia if the dog in question is sick, old, or in pain. Convenience euthanasia occurs when pet owners ask the vet to euthanize a dog simply because their dog has become too troublesome, or doesn't fit into their lifestyle. If there is nothing physically wrong with the dog, and the dog is not a danger to anyone, it can be rehomed. Euthanasia in these circumstances is an extreme solution and many vets will only consider it as a last resort. If a vet believes that a dog can be reasonably and successfully treated, rehabilitated, or rehomed, the vet may say no to euthanasia.