Originally Posted by TrafficTitan

They don't have to stop anybody in a foreign country. All they do is simply make it illegal to do business in the USA if you are a merchant that accepts bitcoins. For example they could say that wordpress.com and namecheap.com can't accept bitcoin payments from US customers. Or they could say those sites can't do business at all inside the US if they accept bitcoins. Consumer confidence in bitcoins then plummets, a rapid sell off occurs, and then bitcoins have little to no value leaving bitcoins a dead currency. The only justification that the USA would need to have for this action is to claim that bitcoins funds terrorism. They can pretty much do anything if they claim it helps terrorists.