Mod Hat On!
Please use the Advanced Search here in the Gun Laws forum. You will find a ton of info on this "hot topic".
Short answer is that there is NO law against it as long as they get a copy of your LTC and C&R FFL. However, the AG has declared that it is illegal for vendors to sell into MA under any circumstances. Last discussion on this topic was either this morning or yesterday!
Most non-MA dealers will refuse to do business with you and WE (NES Management) forbid posting names of dealers who WILL do business with those of us in PRM.