> But why are they then legal to sell?
Things are legal until there is a law or ruling that makes them illegal
Things are legal until there is a law or ruling that makes them illegal
What's illegal is to use insider info to make the decision to do the trade. Did the entity making this trade use insider info? We don't know. If they did not, nothing wrong with the trade.
Now, the circumstances are such that this reeks of insider info. Nobody sane would have done that trade otherwise. So hopefully the SEC will investigate fully. If it turns out the trader really did not have any connection to either of these companies and had no knowledge of the acquisition and simply made the luckiest bet of their life.. then that's fine.
But my point is that there were people on the other side more than willing to take that person's money. If "no one sane" would do that trade, why let the other side be able to profit of it until suddenly it wasn't free money? Why shouldn't the other side carry any risk?
What else would you propose?
Designing an algorithm that prevents people from offering or taking bad trades would require a reliable crystal ball. Solving the halting problem sounds easier.