State laws and locals laws require licensing:
Section 137. (a) The owner or keeper of a dog over the age of 6 months shall obtain a license for the dog. The registering, numbering, describing and licensing of a dog shall be conducted in the office of the licensing authority in the city or town in which the dog is kept.
(b) A licensing authority shall not grant a license for a dog unless the owner of the dog provides the licensing authority with a veterinarian's certification that the dog has been vaccinated in accordance with section 145B, certification that such dog is exempt from the vaccination requirement under said section 145B or a notarized letter from a veterinarian that either of these certifications was issued relative to such dog.
(c) The license shall be granted upon condition that the dog shall be controlled and restrained from killing, chasing or harassing livestock or fowl. The owner of a dog may add descriptive words, not over 10 in number, upon the license form to indicate the color, breed, weight or special markings of the licensed dog. The owner or keeper of a licensed dog shall keep affixed around the dog's neck or body, a collar or harness of leather or other suitable material, to which a tag shall be securely attached. The tag shall have inscribed upon it the dog's license number, the name of the city or town issuing the license and the year of issue. If the tag becomes lost, the owner or keeper of the dog shall immediately secure a substitute tag from the licensing authority at a cost to be determined by the city or town and the fee for the substitute shall, if received by a city or town clerk, be retained by the clerk unless otherwise provided by law. This section shall not apply to a person to whom a valid kennel license has been issued.
(d) This section shall not apply to a dog or cat housed in a research institution.