IMO-approved schemes are “adopted” and come into force 6 months after adoption by IMO.
Before adopting a scheme, IMO considers whether it meets IMO design criteria. Rules for navigation in adopted schemes are as in Colregs Rule 10. Unapproved schemes may lie totally in national waters and are unadopted. Where a traffic separation scheme lies wholly within national territorial waters, decisions concerning routeing lie with the coastal State government. National rules may therefore differ from the international rules.