Can the President of the United States actively invest in the stock market? While I have heard of people often divesting in order to show that they wont profit from the fact they have insider information within the government, I see a lot of politicians still somehow owning stocks and profiteering from their positions within the government, so I would like to know if it is possible for a President to do so politically and legally speaking.
Previous presidents have been obliged to put their investments into blind or at least arms-length trusts. The legal discussion around this centers on the "foreign emoulements clause":
No Title of Nobility shall be granted by the United States: And no Person holding any Office of Profit or Trust under them, shall, without the Consent of the Congress, accept of any present, Emolument, Office, or Title, of any kind whatever, from any King, Prince, or foreign State
and constitutional rules on Presidential compensation:
The President shall, at stated Times, receive for his Services, a Compensation, which shall neither be increased nor diminished during the Period for which he shall have been elected, and he shall not receive within that Period any other Emolument from the United States, or any of them
The paper notes that there are active lawsuits on this question. So it seems that the legal position is "pending decision by the courts", and the political question at the moment seems to be "yes", in that the President's party are unwilling to criticize or take action against it.
Generally, every elected member of the government is expected to put their investment portfolios in blind trusts, so that they cannot actively profit from their position.
But, emoluments aside, requiring it would be a qualification for office in excess of those stipulated in Art. I & Art. II, and would be unenforceable.
It is a norm, though. And usually, public expectation, like revealing historical tax returns, for the sake of getting voters to support you, is enough.