Insider trading feels unfair, but increases the efficiency of financial markets. A price should reflect an estimate of the future profitability of the underlying asset, and insider trading allows those with the most information to have more of an impact on that price.
The Supreme Court is currently considering a case that will determine how broadly to define insider trading. If the defendant loses, then cases where a family member of an insider benefits from a stock tip could be considered insider trading. If he wins, it will probably be much more difficult to prevent insider trading. But why should we?
Some argue that the possibility of insider trading creates a problem of asymmetric practicable information–insiders always know more, but if they’re allowed to act on that information, outside investors lose incentive to invest in potentially valuable projects. That may be, but does it justify prohibiting insider trading? No.
The problem of asymmetric information requires a commitment device, but that device doesn’t have to be one-size fits all. Let businesses and investors solve this problem themselves with contracts.