Your assumption is that there are hobbyists which will now intentionally break the law.
If they are a hobbyists, and now required to get a background check under federal law, they will likely just get a background check rather than stick their neck out for a stranger.
Again - we agree that all sales should require a background check. Not sure why you're so adamant against making improvements when making something perfect isn't on the table.
You need $5? Sorry, I only have $1 on me, do you want that?
NO! I NEED $5.
Start with 1, worry about the next 4 afterwards.