diff --git a/order/order_get_set.go b/order/order_get_set.go
index fb86780..670fa97 100644
--- a/order/order_get_set.go
+++ b/order/order_get_set.go
@@ -11,6 +11,8 @@ import (
 	"github.com/foomo/shop/version"
 )
 
+var ErrorInconsistentStateTransition = errors.New("state transition now allowed")
+
 //------------------------------------------------------------------
 // ~ SIMPLE GETTERS ON ORDER
 //------------------------------------------------------------------
@@ -207,6 +209,16 @@ func (order *Order) SetFraudInvestigationState(state FraudInvestigationState) er
 	if order.Processing == nil {
 		return errors.New("Processing is nil")
 	}
+	currentState := order.Processing.FraudInvestigationState
+	if currentState == state {
+		return nil // state is already set
+	}
+
+	// avoid overriding of "final" states approved and rejected
+	if currentState == FraudInvestigationStateApproved || currentState == FraudInvestigationStateRejected {
+		return ErrorInconsistentStateTransition
+	}
+
 	order.Processing.FraudInvestigationState = state
 	return order.Upsert()
 }