What is the ruling on buying rough diamonds if there is an organization that controls their prices? And is it permissible to circumvent the prices set by this organization by recording invoices for an amount different from what was paid, or by selling to oneself at a different price, or by inflating the price on the invoice and paying the seller a lesser amount?

The fundamental principle in Sharia (definition) is not to fix prices. People are left to trade by mutual consent, based on the Almighty's saying: "O you who have believed, do not consume one another's properties unjustly, but only [in lawful] trade by mutual consent from you." The Prophet, peace be upon him, refused to fix prices when they became high, saying: "Indeed, Allah is the One who sets prices, withholds, expands, and provides." An exception to this is if manipulation or artificial deception occurs in the market, in which case the ruler is permitted to fix prices to remove harm, based on the Prophet's saying, peace be upon him: "There should be no harm nor reciprocating harm." A Muslim must avoid fraud, deception, and misrepresentation in their dealings.