It appears that they are being handled through financial institutions/brokers who are licensed to sell them, since investors from the US would be required to be accredited to buy them. On the other hand, Non-US persons of any financial means are able to buy these without restriction. Thus, making it a much easier sell in Sweden, HK, Malaysia, Singapore, China, etc.
Also, I believe that the Company itself can sell them, but again, they would be required to have you attest to your "Accredited Investor" status if you're from the US.