In a free society a company belongs to its owners--the shareholders--not to the government. The owners have the moral, and must have the legal, right to decide if corporate executives--their employees--will be permitted to trade on or disseminate "inside," i.e., proprietary information. Indeed, the owners have the moral right to decide if corporate executives will even be permitted to own stock in the company.
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Opponents of insider trading claimed that the practice is unfair because information is not available equally to all market participants. For example, if an executive is permitted to purchase stock on the basis of news that he alone knows will increase its value, an "injustice" is done to other shareholders or potential shareholders who do not possess that information.
But by what standard is this unjust? Contrary to the egalitarian premise giving rise to opposition to insider trading, individuals have no more right to information they have not earned than to wealth they have not earned. Should a talented analyst, for example, be forced to make his research publicly available if it would otherwise give him a competitive edge on the market? The mere fact of participating in the financial markets does not confer upon one a right to the hard-won knowledge of others.
In a free market, corporate policy on insider trading would be knowledge available to the public. If a potential investor held that the practice involved too much risk to the value of a stock, he could refuse to purchase the stock of companies permitting the practice. And companies desiring to prohibit the practice among their employees would be free do so by contractual agreement. They would have the moral and legal right to bring civil charges against an executive who violated his contractual obligations.
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Laws against insider trading violate the right of shareholders-owners to decide the manner in which their company will be run. It is right that a company's owners decide what practices their executives will be permitted to engage in regarding the proprietary information that belongs to them.
Sobre o mesmo assunto recomendo também a leitura do artigo Onde está o crime no Insider Trading?, de Carlos Novais.