1. Why Do Ships Follow the Same Rules on the Open Sea?
In the middle of the ocean, there are no visible border lines. Cargo ships from all over the world travel through these waters. The IMO explains that maritime transport carries more than 80% of global trade volume. [10] If every country had different rules, ships would have to change equipment and procedures every time they entered a new port. To prevent this, countries created a common set of promises through the IMO, a specialized agency of the United Nations. [1] The IMO is responsible for ship safety, security, and preventing pollution of the sea and atmosphere by ships. [1]
SAFETY NOTE: The IMO is a UN specialized agency responsible for the safety and security of shipping and the prevention of marine and atmospheric pollution by ships. [1]
2. Why the IMO Cannot Enforce Rules Like a Police Force
The official IMO page states that the IMO itself does not have the authority to enforce treaties. [6] It is not an organization that decides penalties and imposes them on ships. Instead, the rules are made by the member countries themselves. As of October 2026, the IMO has 176 member states and 3 associate members. [4] Additionally, 68 intergovernmental organizations observe the meetings, and 98 international NGOs participate with consultative status. [4]
The Assembly, which includes all member states, meets once every 2 years. The Council consists of 34 countries, though a revision to increase this to 52 countries has been adopted. [5] The Secretariat, located in London, consists of the Secretary-General and about 300 staff members who support these discussions. [5] In short, the IMO is a place where representatives from countries gather to discuss and shape ship rules, rather than a police force that catches violators.
3. How the IMO Was Created by a 1948 Treaty, With Help From Japan
The treaty to create the IMO was adopted at an international conference in Geneva in 1948. [2] However, simply being adopted did not make it active. To become effective, it needed acceptance by 21 countries, including 7 countries with a total fleet tonnage of 1 million tons or more. [3] The treaty entered into force in 1958, and the first meeting was held in 1959. [2] Japan joined in March 1958, and this accession is said to have contributed to the treaty’s entry into force. [3] Japan has served as a Council member ever since. [3] Note that this does not mean Japan was the last country to join. The organization was originally called the Inter-Governmental Maritime Consultative Organization (IMCO) and was renamed IMO in 1982. [2]
4. How Flag States, the Countries Where Ships Are Registered, Enforce the Rules
Implementation of treaties is the responsibility of national governments. Specifically, the "flag state"—the country where a ship is registered—bears the main responsibility for its own vessels. [6] The IMO creates the common rules for everyone, but leaves enforcement to individual nations. This is somewhat similar to the relationship between a committee that writes the rulebook for soccer and the referees who enforce the rules during each match. However, because IMO treaties are agreements between countries, the IMO does not directly police ships in other nations. [6]
There is an exception. Under the STCW Convention, which sets standards for the training and certification of seafarers, the IMO can review the procedures of member countries. [6]
5. How Ship Safety Rules Like SOLAS Are Updated by Implied Acceptance
The SOLAS Convention, which protects human life at sea, had its first version in 1914. It went through revisions in 1929, 1948, and 1960, leading to the current 1974 version, which entered into force on May 25, 1980. [7] The 1974 version introduced the "tacit acceptance procedure." This means that if the number of countries or the total tonnage objecting to an amendment does not reach a specified level, the amendment automatically becomes effective on a set date. [7]
Waiting for a "yes" from every country would take a long time. By allowing amendments to proceed if objections are few, the rules can be updated more easily to match new technologies and needs. This reasoning is an interpretation by the author; it is not explicitly written in the treaty text. [7]
6. How the MARPOL Rules Cut Ship Sulfur Limits by 7 Times
The MARPOL Convention, designed to prevent pollution from ships, was adopted by the IMO on November 2, 1973. Combined with the 1978 Protocol, it entered into force on October 2, 1983. It currently has 6 annexes covering oil, harmful liquids, sewage, garbage, and air pollution. [8]
Under an amendment to Annex VI, effective January 1, 2020, the sulfur content limit for fuel oil used by ships outside Emission Control Areas was reduced from 3.5% to 0.50% by mass. [9] Since 0.50 divided by 3.5 is approximately 0.14, the limit is about 1/7th of the previous amount. [9] Stricter standards apply within Emission Control Areas. [9] This refers to the limit of sulfur contained in the fuel, not necessarily that the actual exhaust emissions dropped by 1/7th. [9] Even though the IMO left enforcement to countries, the fuel rules for ships worldwide changed simultaneously.
7. How to Explore Sea Routes From Products Made Abroad to Japan
Today, you can look at items in your home and find labels that say "Made in [Country]." Use a globe or atlas to trace the sea route from that country to Japan. While the label alone does not confirm if it came by ship, imagining the path across the sea is a good starting point.
If you want to research further, ask: "After the sulfur limit was cut to 1/7th, how did the air over the sea change?" This question cannot be answered by the sources in this text alone. You can find primary sources on the IMO’s official website (in English) under the MARPOL pages. In Japanese, you can also look for maritime explanations from the Ministry of Land, Infrastructure, Transport and Tourism.