This indicates that the interaction from a VTS Centre implies the intention of the sender to influence others by a regulation.
Note: This means that the sender should have full authority to send such a message. The recipient has to follow this legally binding message unless he/she has contradictory safety reasons which then have to be reported to the sender.
Source: IALA Guideline 1068 Para 2, Page 5 (2009)
Vessel Traffic Services
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM