It may be possible to attach a REAL AR15 upper to this toy trigger group and make it fire, but I wouldn’t want to be the crash-test dummy who fires it. The barrel and bolt are contained by the (real) upper receiver, and the lower receiver (the toy part) has only the trigger assembly and magazine holder. I haven’t seen an Airsoft AR15, but if this story is true, it was pretty stupid of the manufacturer to make parts that would fit on a real gun.
The real problem is that the M16/AR15 receiver (the part that the ATF considers the actual “gun”) is a 2 part assembly, top and bottom, and the top part doesn’t have a serial number and can be purchased by anybody because it’s not considered the “gun”.
Of course they don't consider the upper receiver "the gun"; it's just part with the chamber, firing pin and barrel. The untrained, casual civilian firearms owner mistakenly thinks that the muzzle is the dangerous end of such weapons. Fortunately for our society, we have a federal bureaucracy to protect us by regulating and serializing the really dangerous part, the section where you put your finger to pull the trigger. Morons. /sarc