When dealing with US Gov agencies, they can drag you into court from just about anywhere if they want. Just ask El Chapo , or his wife who made the mistake of stepping foot on US soil last month. And while any good prosecutor can indite a ham sandwich, this deal is a bit different.
It's just a lawsuit, with different rules and jurisdictions coming into play. Personally I think they would have to show why they did not go after Craftsman and Snapon to since their tools can be used to remove emission parts. Or Mitchel manuals, cause they sell a book where anyone can look up how to remove an EGR valve..
Maybe a bunch of manufactures and shops should get together and crowd fund a class action suit against the EPA to settle it for all. It's gonna have to go much higher in the courts to get any resolution. If not, they will just continue to pick off of the most popular names one on one..