CT passed a law effective Oct 1, 2019 outlawing 80% lowers. Here is the key section:
Sec. 5. (NEW) (Effective from passage) (a) No person shall purchase or receive or sell, deliver or otherwise transfer an unfinished frame or lower receiver, except as provided in: (1) Subsections (b) and (c) of this section; or (2) subsection (d) of this section; or (3) subsection (e) of this section.
(b) The procedures for the purchase or receipt or sale, delivery or other transfer of an unfinished frame or lower receiver shall be the same procedures as apply to the purchase or receipt or sale, delivery or other transfer of a pistol or revolver under subsections (b) to (e), inclusive, of section 29-33 of the general statutes, provided such purchase or receipt or sale, delivery or other transfer of an unfinished frame or lower receiver is in accordance with the provisions of subsection (c) of this section.
(c) (1) No person shall sell, deliver or otherwise transfer an unfinished frame or lower receiver pursuant to subsection (b) of this section that does not have a unique serial number or other mark of identification, obtained pursuant to: (A) The serial numbering program of the federal Bureau of Alcohol, Tobacco, Firearms and Explosives, or (B) subdivisions (2) and (3) of this subsection.
Their AG made sure to inform all the manufactures of the new law and of CT’s intent to pursue legal action if anyone disobeyed it.