The list goes on, and that doesn't even include the many restrictions on underage activities. So there is nothing unusual or unprecedented about legal restrictions on freedom when an argument can be made that it protects lives or property.
My argument against allowing individuals to invest in stocks is that unless you have insider knowledge, which is already illegal, your odds of beating the index averages are slim. It is nothing more than gambling.
The myth of stock investing is that a person who does more research has better results. But there is no science to support that view. Indeed, the person who understands the most about individual stock investing avoids them completely and invests in ETFs or index funds.
The problem with doing your own research on stocks is that you must rely on the information coming from the management of a company, and managers are generally misinformed or lying. Even the most seasoned investment professionals running mutual funds perform worse than the indexes on average. Brains and research can't overcome the fact that much of your data is deliberately tainted at the source.
When people go to Vegas to gamble, they usually set some sort of limit for their losses. And they go with the full knowledge that winning is unlikely. It makes sense for that sort of activity to be legal, within limits, because it is viewed as entertainment and not investment. But if it were common for people to bet their retirement savings on Blackjack, you can be sure it would be illegal.
We don't allow unlicensed people to practice law or medicine, sell real estate, or even build a house. It is entirely consistent to restrict the untrained from making risky stock investments.
I reiterate that this runs against my own libertarian philosophy. I would feel I had lost something important if I couldn't invest in individual stocks. But it is also true that my net worth would be larger if I had never done it. And it would be larger still if I hadn't allowed professionals to do it on my behalf.
If anyone comments to this post by saying, "I do my own research and I made money in the stock market," it is proving my point. And if you don't see why that proves my point that further proves my point.