What is the ruling on a group of buyers agreeing to distribute fish among themselves in sequence, setting a specific purchase price for the fisherman, and preventing other buyers from entering the bidding, and what is the ruling on participating in or violating this agreement?

The Sharia has prohibited everything that harms or deceives the seller or the buyer, such as Najash (outbidding without intent to buy), monopolization, talaqqi al-rukban (meeting riders outside the market to buy their goods before they reach the market price), and bay' al-hadir li al-badi (an urban dweller selling on behalf of a Bedouin, thus distorting the market).

The method mentioned in the question wrongs the seller and other buyers by monopolizing the commodity. It resembles Najash by pricing the commodity without the intention to buy, and it resembles talaqqi al-rukban and bay' al-hadir li al-badi in that the conspirators exclusively deal with the seller.

Scholars have agreed on the necessity of compelling those who specialize in buying and selling a commodity to sell it at its market price if they prevent others from doing so. This is what Ibn Taymiyyah affirmed, because it prevents injustice to sellers and buyers.

These conspirators restrict buying and selling to themselves, and this is an injustice that must be prevented, or they must be compelled to buy and sell at the market price. They agree to oppress people by taking more than the market price and selling for less.

It is not permissible for these individuals to conspire in the manner mentioned or to prevent others from buying from the seller.