Actually, there are special SEC regulations for stock markets for private companies. There are some extra restrictions on them* but they are there. Look up Gold

Actually, there are special SEC regulations for stock markets for private companies. There are some extra restrictions on them* but they are there. Look up Goldman Sachs trading platform for unregistered securities. * To my (sparse) knowledge, the major restrictions are that only 400 owners max for any 1 company and all investors have to be institutional investors with minimum assets of over $100 million. Still, the traded companies have far lower regulatory requirements.