Gun law in the United States is defined by a number of state and federal statutes.  Sale or delivery of firearms is restricted in Massachusetts like any other U.S. state.  In almost all the states of the US, an importer, manufacturer, dealer or collector shall be licensed under the federal gun control act of 1968 to be a lawful seller. 

No person shall sell ammunition in the commonwealth unless duly licensed.  The chief of police or the board or officer having control of the police in a city or town, or persons authorized by them, may, after an investigation into the criminal history of the applicant may grant a license to any person.  However, no person shall sell ammunition to an alien, a minor, or to a person who has been adjudicated a youthful offender. 

Any lawfully incorporated sporting or shooting club shall, upon application, be licensed to sell or supply ammunition for regulated shooting on their premises.  The secretary of the executive office of public safety may establish such rules and regulations as he may deem necessary to carry out the provisions of this section.

Whoever not being licensed, as hereinbefore provided, sells ammunition within the commonwealth shall be punished by a fine of not less than five hundred nor more than one thousand dollars or by imprisonment for not less than six months nor more than two years.[i]

[i] ALM GL ch. 140, § 122B