What possible legal action can he take? Breach of contract, maybe?
There's no laws regarding cryptocurrency insider trading or manipulation as far as I know.
And it's not a leap to suggest that these cryptocurrencies are going to be treated like securities by regulatory bodies. If the SEC argues successfully (which they seem to be leaning towards) that they're securities, a slew of regulations will begin to apply.
Simply put, you don't need a law that's SPECIFIC to cryptocurrencies in 2017.
That's what makes regulating bitcoin hard. It soon becomes a diplomatic problem.
And there's nothing that these agencies can do to stop the actual wallet-to-wallet transfer short of nuking all miners or knee-capping and getting your private key. So even if you were found guilty, you could conceivably flee the country along with a ton of currency.
Regulation is meaningless without the actual threat of enforcement. It means all exchanges can pick up and move to more friendly countries.
Source: https://gemini24.zendesk.com/hc/en-us/articles/204734485-Is-...