I think your question is impossible to answer at this point. None of us really knows how these exchanges are run and I'm sure not even the owners know what regulation clearly applies to them.
Bitstamp I think has relocated to the UK, and I assume they are being closely watched by regulatory bodies. It would make sense though if there could be some sort of way for people to check the background of these exchanges.
They have an address in UK but are not regulated there. They use a Slovenian branch of Italy's UniCredit and are not subject to UK oversight.