What is the ruling on a grandson's refusal to hand over land that his father gave him so that he would back down from escalating a family quarrel and reporting his uncle to the police, this being after reconciliation?

If the reconciliation is in accordance with the legitimate conditions and by mutual consent of the disputants, then its effects are established by Islamic law, and the dispute is concluded. It is one of the binding contracts from which it is not permissible to retract.