Chapter 140, Section 131G Carrying of Firearms by Non-Residents (this is the MA law that applies. bold with notes by GOAL)
Any person who is not a resident of the Commonwealth may *carry a pistol or revolver in or through the commonwealth for the following purpose of taking part in a pistol or revolver competition or attending any meeting or exhibition of any organized group of firearms collectors or hunting; provided, however, that such a person is a resident of the United States, and has a permit or license to carry firearms issued under the laws of any state, district or territory thereof which has licensing requirements which prohibit the issuance of permits or licenses to persons who have been convicted of a felony or who have been convicted of the unlawful use, possession or sale of narcotic or harmful drugs; provided, further, that in the case of a person traveling in or through the commonwealth or by the state of his destination.
Police officers and other peace officers of any state, territory or jurisdiction within the United States duly authorized to possess firearms by the laws thereof shall, for the purposes of this section, be deemed to have a permit or license to carry firearms as described in this section.
*as used above, “carry” actually means possession of a firearm, unloaded, and locked in a case. This does not mean that an out of state resident can carry concealed or otherwise on his or her person without a MA LTC. The firearm must remain in the case until such time as the competition, hunting, etc. is taking place
Traveling to other states?
Check out Handgunlaw.us, a great site with an interactive map that show licensing requirements, as well as licensing information for every state.