I have been saying that for a long time, fiat is absolute poison.
That's why you should not use fiat money at all. Don't exchange bitcoin for fiat. Just use bitcoin as money. Buy and sell stuff. And fuck goverments and banks.
In the USA, he would have to register for a MSB license (Money Services Bussiness) from the Treasury Department. That is probably all they got on him, which is why he was arrested. Kind of like running a bar without a liqour license, not doing anything illegal but you need a license for that business.