Your comment depends on the interpretation of the word 'free' in 'free market', and it's why many economists would argue that anti-cartel legislation that makes actions like this illegal is necessary to protect the free market.
ie. A market can become less free through bad government regulation which limits competition, but it can also become less free through the collusion of some market participants in a trust which limits the ability of other participants to truck barter and trade.
ie. A market can become less free through bad government regulation which limits competition, but it can also become less free through the collusion of some market participants in a trust which limits the ability of other participants to truck barter and trade.