Nothing stops an unaccredited investor betting the farm on Enron. If there is a less perceived risk, people will use more leverage. So all of this "protection" just amounts to restricted opportunity.
Several people went to federal prison and Arthur Anderson went out of business over the Enron shenanigans. This seems as much a deterrent as the Securites Act of 1934. If you’re willing to risk federal prison, you can solicit non-accredited investors for unregistered securities.