The current federal government in the USA actively encourages federal agents to use illegal and unethical methods, and promised them protection and immunity.
The FBI is the primary party appearing to be in this investigation, and to the best of my knowledge are both of the US (govt), and are federal. (I'm not a US person so please correct me if I'm wrong.)
The article mentions the FBI investigation but is not about that. This article is about a pressure campaign, the letter Web Abuse Association Defense sent to adguard making threats under french law and adguard's investigation in response to that letter.