Their crypto pyramids schemes and pump and dumps were also technically legal in the US (I am assuming). And yet it is impossible for a pyramid scheme to work, can any US lawyer or judge show how a pyramid is viable? Of course not, because they are scams.
You have "technically legal" schemes in other countries too. If there is a desire to address criminality a way can be found.
If you want to achieve something, coming up with excuses around why it is not possible rarely bring results.