Since you've mentioned about darknet and FBI, makes me wonder in which country was Chip Mixer established?
ChipMixer is not established in any country. As btce arrest show - if US wants to close you down they dont care where you are or what law protection you have.
The thing with anonymous mixers such as the late BitMixer and the current ChipMixer is that there is absolutely no way to tell if money is being laundered.
ChipMixer does not "launder money". ChipMixer transforms bitcoin transactions into fungible, same size chips breaking transaction history. ChipMixer privacy protection is like an encryption. You do not need to do anything illegal to want privacy. Do you believe when government says that "only terrorists use encryption"? It is the same with "only criminals use mixers".
Money laundering is loosely defined crime against government. They want to know how much you earn and what you do. If you hide it, you are a criminal. For example if you are an American citizen and you live and work for 20 years in Thailand you have to report to Uncle Sam your thailand earnings (and pay your income tax for US). Government owns you and a share of whatever you earn. Is this slavery illegal? No, money laundering is.