Not end of story. Your grasp of the situation remains incomplete. There is no magical category below the legal joule/fps definition of real firearm. When a device fails to meet the joule/fps requirement, it can be one of two things. It can be an Imitation Firearm or a Replica Firearm. Imitation Firearm is a category that include all things meant to shoot like real guns but do not closely resemble real guns, ex. paintball markers. Replica Firearm are things that very closely resemble real guns, and Replica Firearms are considered Prohibited Devices, which are controlled Federal law (Criminal Code).
If you read the CITT appeal, the emphasis is on
resemblence to real firearms, because it is that resemblence that makes airsoft guns Replica Firearm and a Prohibited Device. They spend most of each report emphasizing the resemblence.
It is inconsequential in the Criminal Code that airsoft guns also shoot, because they do not meet the criteria for real guns. The current law only cares if a gun shoots hard enough to be a real gun. If it does not, then the question is whether or not it is a Replica Firearm, not whether or not it shoots all. The current law is not written to protect people from guns with unsafe joule/fps, only to protect us from deadly ones. For example, paintball markers regularly break the 5.7J limit, but are not considered real firearms. Still, if you
attempt to import say, a RAP4, which closely resemble a real firearm, it is treated as a Replica Firearm and a Prohibited Device. This is despite the fact that according to the law, based on the muzzle energy criteria, RAP4 is not a Replica Firearm but in fact a real firearm (though not a real M4, because it is not cartridged or centrefired).