It might be necessary to create a legal basis, but it's just a matter of doing it. If the owners don't like it they can dissolve it.
Tell me you don't know anything about the law without telling me
That's not the sole reason. They (should) also enforce a fair even playing field by preventing market manipulation (e.g. how Elon was tweeting about stock prices) and a few other things to "facilitate efficient markets and the formation of capital".
> Why should SEC rules apply?
Because private companies still fall under the jurisdiction of the SEC? See e.g. Theranos.
> On what legal basis can you force a private company to divulge its financial details?
On the to-be-created legal basis that aims to prevent bubble formation and the resulting fallout to the wider society?
> Would you be happy if you, as an individual, have to divulge your account statements if your own net wealth reaches one million?
Sure, why not? It's not a totally unheard of idea. In Norway everyones salary can be looked up.
if you're smart.
I don't think this is an SEC problem, they are fully aware that people subject to their jurisdiction can jump through many hoops to circumvent them. This shows consent on the investor's part well enough, and capital formation regulations do not burden the investor at all, they are only constitutional because they burden the organization raising capital, who simply needs to do a cursory check - not an in-depth one. (level of depth is based on which regulatory exemption is chosen)
So as long as you separate concerns the SEC is satisfied.
the friction that the whole industry and the SEC pushes and pulls on is that nobody wants to go public because it's needlessly expensive to be a public company, companies would otherwise go public
basically, one publicly traded company does something egregiously bad, the SEC mandates a new expensive disclosure that requires a completely new operating style, less companies go public
the SEC's mission statement is a dual mandate: provide for fairer securities markets (via transparency mandates), and the second one is facilitate capital formation
so when the goal of providing for fairer markets is hampering people raising and accessing capital at all, then they help on that front
in this case, as people avoided going public, they would run into the number of investor limits and do suboptimal things because they couldn't raise more capital. so the limit went up to what it is
now, with that foundation in mind, your main point isn't close to what's happening "if a company is big enough it is important to reel it in a bit or else shenanigans happen", the SEC doesn't "reel in big companies". it mandates transparency in public companies, number of investors in private companies, and regulates details of certain transactions, that's it. you can be any size. they don't judge the merit of an investment (outside of some ETFs, since they also regulate fund advisors and ETFs just happen to be publicly traded funds), the SEC's focus is that there's enough information for an investor to judge the merit of a publicly traded investment