Earlier quoted context omitted.
And taxing it enough ensures those black markets don't disappear.
Regulations is a secondary taxation on legal dealers. Businesses have to pay high license fees, buy required security, keep records of EVERY PLANT (rfid tags). Its still profitable enough and safe enough from police harassment that there about 900 businesses.
[1] http://www.cnbcprime.com/marijuana/video/pot-after-hours-the...