For those who don't believe in ghosts

[discntnt_irny_srcsm]

2. Things evolve

Pennsylvania state police told to treat 'ghost guns' parts as firearms
https://6abc.com/pa-state-police-told-to-treat-ghost-guns-parts-as-firearms/5759965/
Democratic Attorney General Josh Shapiro issued a legal opinion to the Pennsylvania State Police that the gun frames, also known as "80% receivers," qualify as firearms.
...
"No single factor is dispositive," Shapiro told Evanchick. The police "must weigh all the applicable factors together to determine whether a receiver 'may be readily converted' to expel any projectile by the action of an explosive."

Shapiro said the guns are increasingly being found in the hands of people who are barred from possessing firearms. He said the attorney general's office found felons purchasing the kits at recent gun shows in the Philadelphia suburbs, York and Harrisburg. More than 100 ghost guns have been seized from prohibited purchasers in Philadelphia this year, he said.

I does make more sense to me to consider the function of the component items rather than taking the step requiring the manufacturer to serialize anything which qualifies as an 80% unit.