Since they are netting in Ct. but transporting to Mass. that becomes interstate commerce and under any Federal laws having to do with bunker, selling bunker, etc.
Also, what are the Mass laws? When you travel to Block Island from Mass to fish and return to Mass your catch has to be legal in Mass. So returning to Mass. with bunker that possessed bunker must conform to Mass. law. Does Mass. have any bunker laws like a limit for individual use, the requirement for a Mass. license, a Mass. commercial netting license to possess over X amount of bait, etc. Find out where they go in Mass. and file a complaint in Mass with all of the location and license plate info. Just some thoughts.