Mass. Gen. Laws ch. 161 § 95
Whoever without right enters, remains in or loiters within a station, waiting room, or terminal of a public transportation facility, or upon the platform, stairs, grounds or other premises of a public transportation facility, after having been forbidden so to do either by notice posted thereon, or by the person who has the lawful control of said premises, or by a railroad, railway or railway express officer or by any police officer, shall be punished by a fine of not more than one hundred dollars and may be arrested without a warrant by such officer and kept in custody in a convenient place, not more than twenty-four hours, Sundays and legal holidays excepted, at or before the expiration of which time he shall be taken before a proper court or magistrate and proceeded against according to law.
Mass. Gen. Laws ch. 161, § 95