The SEC rule 501 (not 59) prohibits a company from selling an unregulated/unregistered security to public investors. But it doesn't prevent US public investors themselves to go and buy these securities through foreign exchanges (not sure about exchanges registered in the United States). So the terms and conditions are usually to protect the company (in this case EOS) from any litigation. But under certain exemptions these securities can be sold to 'Accredited' US investors.

Basically, what needs to be understood is that US investors are protected from any security fraud by having rules that prevent company's from selling unregulated securities.