Insider trading is theft. You know the stock will go up, the other party unfairly doesn't. The other party would not have sold if he had known, so you have che

Insider trading is theft. You know the stock will go up, the other party unfairly doesn't. The other party would not have sold if he had known, so you have cheated the other party. Same if you know the stock will go down. The other party would not buy if he had known the thing you unfairly do. This is also cheating someone. Buying a rivals stock depends on the reason why, but it would be against company interest. The SEC doesn't need to enforce this, the board should fire him for it.