The article you have supplied has several comments by posters and answers back from the inventor, himself. He also supplies additional information for the readers. There’s also another guy there, who comments on an invention that the BATF said was illegal, too (he said back in 1989). He sold his invention to another guy who happens to be still making it (apparently without any problems) and making a lot of money off it.
So, it appears that if someone wants to fight these things and go ahead anyway, they probably can and fend off the BATF. It is apparently not a matter of illegal or not, but rather if one is willing and has enough money to continually fight the government, even if the government is doing the wrong thing. They can bankrupt a person by simply continuing to do the “wrong thing” and running you into bankruptcy trying to defend yourself.
At any rate, this sounds like something that the BATF has done illegally and they are simply “pushing their weight around”...
Regards,
Star Traveler
Any firearm banned is potentially unconstitutional in the first place.