I must respectfully disagree. I am not a Lawyer but the English Language meaning of Sections 121 and 131 are crystal clear. I also respect Atty. Jason Guida but disagree with his assessment posted earlier.
Section 121 of Chapter 140 Contains DEFINITIONS. It defines among other what an "assault weapon" is. The verbiage in definition "f" of assault weapon has had the date July 20, 2016 added to now mean that any firearm that contains the features outlined in "a" through "e" is not considered and assault weapon if it was legally owned and registered prior to July 20, 2016 (i.e. the Healy Enforcement Notice). So it is "grandfathered" in regards to the definition and is not even an assault weapon. This of course means that firearms purchased after July 20, 2016 are in fact considered assault weapons by definition.
Section 131 of Chapter 140 deals with the Conditions and Restrictions associated with the issuance and possession of an LTC. Section 131(M) used to talk about expired licenses and has totally been replace in the new law with the restriction against possessing, owning, selling, and transferring assault weapons. Section 131(M) clearly states in subsection (a) that you cannot possess, own, or sell and assault weapon. Subsection (b) clearly states that subsection (a) does not apply to any assault-style firearm lawfully possessed on August 1, 2024 by either an LTC holder or an FFL.
I have not taken the time to verify that "holder of a license to sell under section 122" means FFL but I am assuming it does. If it does not I apologize.
To summarize - If you owned a assualt style firearm prior to July 20, 2016 it is grandfathered as to actually being defined as an assualt weapon and is therefore not subject to any laws regarding owner ship of assualt weapons. If you actually lawfully owned and registered a firearm that meets the definition of assualt weapon prior to August 1, 2024 it is grandfathered as to legality of owning, possessing, selling, or transferring. Discussions regarding "what is lawfully owned" or "but there is no registration" are moot and change nothing above.
Again I am not a lawyer but I'm also not an airsoft player masquerading as a gun owner.