Updating Existing Sales Order Item Locations

I tried to update Sales Order item locations in Netsuite through web services using the below code but I always get the same error message listed below. Is it even possible in Netsuite to change Sales Order item locations after they've been created? (logOperator just writes to console).

RecordRef salesOrd = new RecordRef();
   salesOrd.internalId = "46998";
   salesOrd.typeSpecified = true;
   salesOrd.type = RecordType.salesOrder;
   ReadResponse read = _service.get(salesOrd);
   if (read.status.isSuccess)
   {
    SalesOrder ord = (SalesOrder)read.record;
    foreach (SalesOrderItem item in ord.itemList.item)
    {
     RecordRef locRef = new RecordRef();
     locRef.internalId = "9";
     locRef.type = RecordType.account;
     locRef.typeSpecified = true;
     item.location = locRef;
    }
    SalesOrder order = new SalesOrder();