If you are licensed to carry firearms in another state and you move to Massachusetts, you will need to comply with the Massachusetts gun laws. For instance, you will have to seek a license or FID card in Massachusetts in order to be in possession of a firearm in Massachusetts.
It is important to understand that having a license to carry in another state is insufficient for firearm possession in Massachusetts. What may be legal in another state could immediately subject you to an 18 month minimum mandatory sentence in Massachusetts.
Insufficient knowledge of the firearms laws in Massachusetts is also not a defense. It is important to consult with a criminal attorney who handles firearm cases regularly.