Mass. Gen. Laws ch. 140 § 139A
No shelter shall sell or give away any dog or cat that has not been spayed or neutered, unless a written agreement is entered into and a deposit of not less than $40 for spaying or neutering such dog or cat has been tendered to the shelter. The shelter may make appropriate arrangements for the spaying or neutering of such dog or cat by a licensed veterinarian, or may return the deposit to the person purchasing or receiving the dog or cat upon presentation of a written statement or receipt from a veterinarian or clinic that the dog or cat has been spayed or neutered by a licensed veterinarian.
Any dog or cat six months of age or older at the time it is sold or given away by the shelter shall be so spayed or neutered within sixty days, or the deposit shall be deemed unclaimed. Any dog or cat under six months of age at the time it is sold or given away by the shelter shall be so spayed or neutered within sixty days after reaching six months of age, or the deposit shall be deemed unclaimed.
Any deposit not claimed under this section shall be used only for the following purposes:
A shelter may enter into a cooperative agreement with another shelter and with a veterinarian in carrying out the provisions of this section.
The commissioner may set fines for violations of this section and may further establish regulations to ensure compliance with this section. Additionally, an animal control officer, an officer licensed under section 57 of chapter 22C, a police officer or the owner, director or a duly authorized agent of an animal shelter from which an animal was obtained may bring a petition in the district court within the judicial district in which the dog or cat is owned or kept for an action of forfeiture and relinquishment of ownership. Legal fees or court costs incurred in the enforcement of this section shall be the responsibility of the owner of the animal.
Mass. Gen. Laws ch. 140, § 139A