Answer
A. Convention
A Convention is a formal international treaty concluded between States establishing legally binding rights and obligations once the required entry-into-force and ratification/accession conditions are satisfied.
Examples:
- SOLAS 1974
- MARPOL 1973
- STCW 1978
- MLC 2006
- Load Line Convention 1966
- BWM Convention 2004.
B. Protocol
A Protocol is a separate treaty instrument normally used to:
- supplement;
- modify;
- update; or
- introduce major changes to
an existing convention.
It usually has its own:
- adoption date;
- ratification conditions;
- entry-into-force criteria.
Example 1 — MARPOL
MARPOL was originally adopted in 1973.
Following major tanker casualties, the 1978 Protocol was adopted.
Because the 1973 Convention had not yet entered into force, the 1978 Protocol effectively absorbed it, resulting in what we normally call:
MARPOL 73/78
The combined instrument entered into force in 1983.
C. Amendment
An amendment changes one or more provisions of an existing convention, protocol, code or annex without necessarily creating an entirely new convention.
Examples:
STCW Manila Amendments 2010
These substantially revised training, certification and watchkeeping requirements.
IMO explains that amendments are required because technology and maritime practice change rapidly and that SOLAS, MARPOL and COLREG use tacit acceptance procedures for many amendments.
Tacit acceptance
Instead of every country formally accepting an amendment individually:
The amendment is considered accepted after a specified period unless objections are received from the required number/tonnage of Contracting Governments such as one third of the member countries or nation holding half of the world's merchant ship tonnage.
This allows SOLAS and MARPOL amendments to enter into force much faster.