Example: you are an executive at E Corp and the company will announce its acquisition in two months. You had previously set up planned trades to sell x number of shares each month before then. Because the acquisition is at a premium on the current price, you will make much less money if you go forward with your trades before the announcement. So, what do you do? You cancel the trades.
Was this insider trading according to the SEC? Surprisingly, no! Even though you're profiting from insider information, the SEC rules are such that for insider trading to occur, you actually need a trade.
https://en.wikipedia.org/wiki/SEC_Rule_10b5-1#A_possible_loo...
Martha Stewart did exactly this before her company was acquired earlier this year: