A criminal investigation authority may refrain from intervening in the transport or other delivery of an object, substance or property or transfer such intervention if that is necessary in order to identify persons participating in an offence that is being committed or in order to clarify an offence or larger offence entity that is more serious than the offence that is being committed (controlled delivery). Furthermore, a criminal investigation authority may use controlled delivery if there are grounds to suspect an offence for which the most severe punishment provided is imprisonment for at least four years. This four-year-requirement applies only to domestic controlled deliveries, not to international controlled deliveries, since in international cases the applicable convention prevails.