 This is of course not allowed by the local regulator and also the receiving carriers prefers the higher international rates, but since the black action is done in a switch owned by a person or company who is willing to break the law, this is usually outside of the view of these parties and thus enforcement can be difficult.Grey routes can be prevented by good Fraud Management or by regulators or carriers opting to close the gap between the international and domestic tariffs.Tariffs are usually a maximum and thus sometimes carriers opt to lower the international rates to prevent grey routes.