The only argument I'll buy is that public regulation of insider trading is improper, and that such should be left to private agrieved parties.

But I can perhaps buy some of these arguments, in that people with private information are acting in the very best sense of capitalism. Someone who knows through industry contacts that a company is operating inefficiently is free to start a competing company. Why then should they not be free to divest themselves of shares in a company they no longer feel they can support?

I'm not firm on this position.

I do think that public regulation is bad, generally. At most, laws should provide for full disclosure of the nature of a good or service, and someone who has been decieved should sue.

If a company is lieing about their preformance, and does so after they definatly know that it is untrue, then this should be actionable. That they sell stock while touting the companies position in the market, like enron did after it was clear the company wasn't doing as well as they claimed, then this could be evidence of improper advertising of the company.