Can the president be investigated by the SEC for stock manipulation? This year the SEC investigated Elon Musk for possible stock manipulation through social media posts, and he was ordered to stop making tweets related to his business. Today, Trump made a post that led to a major drop in the stock market. This wasn't the only time he made a post that impacted the market. Is it possible that the SEC tell the president to stop tweeting and investigate for stock market manipulation?
If you would make it illegal for celebrities to make statements which could affect the stock market in any way, you would make Twitter illegal in the first place. Especially for politicians, because everything politicians say or do can indirectly affect the stock market. Whenever a politician publicly suggests that some industry should be regulated, taxed or subsidized more or less than it was before, the stocks of the affected companies will react to that news accordingly. But making public statements about political intentions is important for a democracy, because it is the only way to have a public discussion about policy or for voters to make informed decisions about who to support.
The reason why the SEC complained about Elon Musk's use of Twitter was because he made statements about companies he managed or was a shareholder of which were allegedly fraudulent.
How would this apply to the US President?
- The SEC would only have a right to complain about manipulating stocks in a way which financially benefits the US President himself. They can't blame the US President for any other stock manipulation. This is, by the way, one reason why many US government officials put their private investments into a blind trust while they hold office. That way they avoid allegations that their political statements or decisions benefit their own investments. However, Donald Trump decided to not do this.
- There was an important court decision in 1867, Mississippi v. Johnson, where a court decided that the US Presidents are not within the reach of judicial direction when they exercise their presidential powers. Is making political statements via Twitter a part of the exercise of power of the US President? In the 21st century, probably. But I am not aware of any actual court decisions in this regard.
- It is questionable if a federal commission is able to indict a sitting president for any crime as long as they are in office, including for misdemeanors they committed before they took office. The conclusion of Robert Mueller's report was that this is the sole prerogative of Congress.