A free market is one where two or more parties are free to exchange goods and services voluntarily, thereby determining prices through the forces of supply and demand. The nature of these transactions must be voluntary in order for it to be considered free market exchange.
So, in my view, your question the following: is there a time when two or more parties wish to voluntarily exchange goods or services, but given the circumstances of the exchange, government has a duty to forcibly intervene, thereby preventing the exchange?
Many are tempted to point to fraud, pollution, or other unjust conduct as evidence that the free market does not work. However, each of the examples that one could give would involve an exchange where one or more parties did not voluntarily engage in that exchange, and therefore, the injured party would have a right to seek damages from the offending party. In a free market, I am no more justified in destroying your garden or selling you snake oil as a cure for cancer than I am in any other market system.
Therefore, I maintain that there exists no exchange that warrants government intervention given that all parties involved engage in the exchange voluntarily. We should conclude that the free market is good for the public and that it is the only market system that equally and evenly respects the rights and autonomy of all members of society. To that point, I conjecture that it is immoral to forcibly intervene in such an exchange since doing so would obstruct the autonomy of two or more moral agents, which I believe to be supported by Immanuel Kant's Categorical Imperative.