Mass. Gen. Laws ch. 131 § 88
The director, his deputy directors of enforcement, chiefs of enforcement, deputy chiefs of enforcement, environmental police officers and deputy environmental police officers, wardens and members of the state police in areas over which they have jurisdiction may request any person whom he reasonably believes to be engaged in hunting, fishing, or trapping, or to be unlawfully in possession of fish, birds or mammals, or to be in possession of fish, birds or mammals unlawfully taken, or in possession of unlawful equipment or ammunition, to forthwith display for inspection all fish, birds, mammals, equipment or ammunition then in his possession, and may arrest without a warrant a person refusing or failing to comply with such request.
Mass. Gen. Laws ch. 131, § 88