Current states with special clauses or prohibiting the sale of Lower Receivers are:
WASHINGTON:
Effective July 1, 2019, Washington state passed House Bill 1739, banning the sale of polymer 80% Lower Receivers. As of August 1, 2021, (to Bilson Arms knowledge) aluminum Lower Receivers are allowed to be purchased and sold.
https://app.leg.wa.gov/billsummary?BillNumber=1739&Year=2019
NEW YORK
February 14, 2020, New York passed S.7763-A/A9903, the Jose Webster Untraceable Firearms Act banning the sale and ownership of 80% Lower receivers.
https://www.nysenate.gov/legislation/bills/2019/s7763
CALIFORNIA
Assembly Bill 857 requires all Lower Receivers have a serial number. Under this law, a resident must apply for a serial number via the California Department of Justice with the serial number being registered and engraved on the receiver or frame of your Lower Receiver.
https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=201520160AB857
HAWAII:
On September 16, 2020, HB 2744, passed without the Governor’s signature makes it a Class C felony to purchase, manufacture, or otherwise obtain firearm parts for the purpose of assembling a firearm with no serial number. It also amends certain parts of previous firearm registration. (SD2)
https://www.capitol.hawaii.gov/Archives/measure_indiv_Archives.aspx?billtype=HB&billnumber=2744&year=2020
CONNECTICUT:
Under Substitute House Bill 7219, Public Act 19-6, all Lower Receivers must be labeled with a serial number. The serial number is to be engraved on them before manufacturing. Further, no polymer receivers are allowed, and transferring “ghost guns” is prohibited except to law enforcement.
https://www.cga.ct.gov/2019/BA/pdf/2019HB-07219-R01-BA.pdf
And finally, effectively banning all sales and ownership of Lower Receivers,
NEW JERSEY:
As of April 2016, per (former) Attorney General, Gurbir Grewel, New Jersey citizens are not allowed to sell or own Lower Receivers.
https://www.njleg.state.nj.us/2018/Bills/S2500/2465_R1.HTM