Acts are the highest level of UK law.  They contain fundamental requirements and often grant power to Government Ministers to create more detailed regulations.

These contain the majority of UK laws.  Statutory Instruments are created on the orders of Government Ministers who have the power granted by Parliament, by an Act.

Merchant Shipping Notices (MSNs) are used to convey mandatory information that must be complied with under UK legislation. These MSNs relate to Statutory Instruments and may contain technical detail pertaining to such regulations.

Marine Guidance Notes (MGNs) give significant advice and guidance relating to the improvement of the safety of shipping and of life at sea, and to prevent or minimise pollution from shipping.  They may relate to a specific international, EC or UK requirement.

Marine Information Notes (MINs) are intended for a more limited audience e.g. training establishments or equipment manufacturers; or contain information which will only be of use for a short period of time, such as timetables for MCA examinations. MINs are numbered in sequence and have a cancellation date (which will typically be no more than twelve months after publication).

Conventions are legally enforceable rules agreed internationally at IMO and are implemented via UK regulations.  

EC Regulations and Sirectives are legally enforceable rules adpoted by the Member States and implemented via UK Regulation.