How are they not a firearm? If you mean the pre-made kits sure, but once done: gun. Goes bang. Just because not subject as yet to the NFA or GCA doesn't mean not a gun. In fact, federal law prohibits felons (and misdemeanor DV convicts) from owning firearms of any sort, including home-made ones; they are legally guns.
Similarly, if you make a suppressor or a machine gun, doesn't matter if it's from a block of metal at home and for personal use so you don't fill out the proper paperwork. Violation and federal prison.
Random thoughts:
- Ghost Gun is a loaded word to make home made gun (or craft made or for personal use or whatever proper term we want) sound scary.
- "80%" is just us talking, not an ATF designation, ruling, open letter, or anything (that I am aware of). They could formalize what makes a gun a gun. It could be a LOT less of a gun all of a sudden.
- They could decide that the kits to do this are intent or whatever let them get rid of stuff like the two adjacent tables at the gun show that let you, together, make a lightning link.
- They could change the rules on home-made guns. So far there are a few localities (and one state at least) that require marking, registration, and so on for them. It would not seem a super longshot to require the same at the federal level.
Much of this could make interesting court cases, but that's a ways off.
Everyone, please correct anything I got flatly wrong!