The law requires the gun to have a 10-lb. trigger when the dealer sells it originally. Actually, S&W assigns certain SKU numbers to the "MA Compliant" guns that can be sold here. (See their web site catalog.) After the original sale, the owner can change out the trigger. The Apex is popular. Any guns sold new in MA must pass a series of tests, and even then the attorney general can refuse to certify them. No other firearms are illegal to own, as long they don't have "Assault Weapon" features. But they can't be transferred by an FFL. They can be bought by a licensed person from another licensed individual. It all makes sense to our overlords in Boston.