My google-fu is not finding the news source. But a poster at Subguns says:
ATF goes after airgun suppressor mfgs
Recently the airgun world has been pushing the limits of the law to the point of making aluminum body suppressors with monocore baffles and versions of aluminum k baffles.
The old ruling was if the suppressor was permanently attached, if it couldnt be used on a firearm it was OK. Well some idiot in FL started making and marketing ones that easily work on a rimfire (he puts the words airgun only on them) and some idiot in CT got popped for using an airgun suppressor on CZ rifle with an adapter going 1/2 28 to 1/2 UNF (sold by the same company) to allow you to use the suppressor on rimfires where legal.
Another company has started making the same style suppressors and decided to name them after old SWR suppressors. A new Trident suppressor is out and its airgun only but I guess a guy in MI figured out it works on rimfires. WTF people