Galdo claimed that he was entitled to the land because of “adverse possession” — a legal doctrine that allows someone who doesn’t own a property to still claim it by proving visible, continuous possession for 21 years. According to Galdo, he had, at the time, maintained the property for nearly 25 years. The city, in contrast, said that because it had acted on behalf of the commonwealth to aid I-95′s construction, it was therefore protected by the immunity that shelters the state from adverse possession claims.