This is basically want public equity markets are. You have to be an "accredited investor" (the only requirement is having a lot of money) to invest in all the extra risky things.
That's a US thing. In the UK there's a KYC type form you fill out, self-certifying that you know what you're doing. And then you can trade CFDs, which are illegal in the US accredited or not. (Or not approved by regulators I suppose I mean, I assume professional US desks trade them OTC 'in' Europe. But I think probably European brokers even can't market them to or allow trades by US retail customers?)