Let's be clear, I am no lawyer and I always follow the laws in all things.
This is just speculation. A company, not based in the USA, whose principals (CEO, etc.) is not living in the USA, and whose assets are not in the USA would be pretty hard to stop or prosecute if it was being traded on a networked, distributed exchange.
Sure, one government could put pressure on another, but if there is are guns, drugs, slavery, transportation of people, or use of regular fiat type banks, it will be pretty hard for the SEC, on a practical level, to do very much.
Now, I would never suggest that anyone take my legal advice. I will provide you with advice on theology, psychology and dating, but this is just theoretical speculation.
Data is data. A message sent to a blockchain representing a ledger is just data. It will be fun to see which clever software/financial guy finds a way to circumvent national boundaries and national laws.
On the other hand, I am glad that the EPA, FDA and SEC exist. While I do believe that individuals have the right to make their own informed decisions, there are plenty of scammers and people out there for whom law and ethics do not matter at all and from whom protection is required.
Political boundaries are melting. While Bitcoin is politically agnostic, there are some implications involved in the Satoshi legacy. If currency or value can be transmitted across borders, that will mean that borders are artificial. One of them is that if there is a worldwide computer network in which data can be sent from individuals living in countries whose governments are ostensibly at war or at least not in diplomatic relationship, then perhaps, the exchange of information and commerce between the individuals can circumvent the rigidity and stupidity of their respective governments, and thereby, somehow, due to the commerce and communication between individuals bring about a better world.
I look forward to how some clever software guy or girl finds an elegant solution to the SEC/stock exchange problem and hope that this person is not discourage out of fear of rigid existing governmental systems.
People need to understand that the SEC rules are very strict on shares which can be traded. Any company planning a colored coin or web system is going to fall foul of all the same issues as BTCT and Bitfunder unless they are fully SEC compliant.
Any company allowing their shares to be traded (by US citizens) in this way via a third party - same problem.
They simply cannot be traded without being an issue for the SEC and it could be an issue with the security itself and not the trading platform (well, that too).