Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 138, § 56

A deputy sheriff, chief of police, deputy chief of police, city marshal, deputy or assistant marshal, police officer including a state police officer, or constable, or, in the county of Dukes or Nantucket, the sheriff anywhere within his county, or any investigator of the commission, may without a warrant arrest any person whom he finds in the act of illegally manufacturing, selling or exposing or keeping for sale, storing, transporting, importing or exporting alcoholic beverages or alcohol, and seize the said beverages or alcohol and any vessels and implements of manufacture or sale in the possession of such person, and detain them until warrants can be procured against such person, and for the seizure of said beverages or alcohol, vessels and implements, under this chapter. Such officers shall enforce or cause to be enforced the penalties provided by law against every person who is guilty of a violation of this chapter of which they can obtain reasonable proof, and shall make all needful and appropriate investigations for the said purpose.