I'm confused, law suit - suing them, vs, legal charges?
If they have evidence of a violation of the law, then bring charges and the ATF can investigate and shut them down if it can be proven.
This guy may or may not be a legit business, if he is breaking the law, catch him, and take him to court.
If there is no evidence, then, this feels like a "we cant prove anything, so we are going to smear you in the papers" or try to get an out of court settlement (which may be a methodology used by anytown in the past from what I have read)
I believe we have seen other folks, businesses, police, politicians, etc fall under this same microscope in the recent past - court of public opinion, trial by press, misdirection to throw off blame, whether true or not.
just my initial impression
D