Carl Icahn, corporate raider, helped the incoming Trump administration to select cabinet nominees, particularly succeeding when the Senate acquiesced in the case of now-EPA director Scott Pruit. In the process, while acting as an unpaid adviser to the President, Icahn might have made a killing by shorting EPA-mandated renewable energy credits which one of his oil companies had been buying. Whether this constituted a legal offense is uncertain.
The story is covered in the New Yorker magazine. I would suggest that anyone interested in supporting the professional journalism which is currently carrying the water for the Republic should read the article in its entirety, and support it, perhaps by subscribing, buying the current edition, checking it out in the local library, or citing it on social media.