The hard part is that US citizens may not know they are doing business outside the jurisdiction of the US government. Are you rejecting the protection of the US government if the company is doing its best to obscure that fact and the associated risks? How about if they are advertising in the US? On the superbowl?
If they're putting life changing amounts of money into a company they should be doing a modicum of research on it. If someone gives $100k to a Nigerian prince, I don't think the US government should be spending thousands of dollars of resources on attempting to recover that money.
US citizens have never implicitly been allowed on these off-shore exchanges. You have to deliberately circumvent and lie to get an account.
