Suppose that, as an insider in Company A, I become aware of an upcoming business move by Company A that will have a huge negative impact on its share price, and a similar huge positive impact on the share price of Company B, the only major competitor to Company A. (Think just ceasing operation without any public warning.)
Clearly I can't dump my Company A stock, or short sell Company A, without violating insider trading regulations.
But can I buy a bunch of Company B? I have no insider information on Company B, or do I?