What rules govern international waters?

The geopolitical and legal status of the Strait of Hormuz has come under scrutiny following tensions between Iran and the United States over freedom of navig...

What Happened

The geopolitical and legal status of the Strait of Hormuz has come under scrutiny following tensions between Iran and the United States over freedom of navigation in this strategically vital waterway.
Iran has asserted a right to restrict or charge tolls for transit through the Strait, which it partly borders, invoking sovereign rights over its territorial waters.
The United States and most of the international community contest this, arguing that the Strait of Hormuz is an international strait governed by the "transit passage" regime under UNCLOS, which cannot be suspended.
The dispute exposes a fundamental tension: both Iran and the United States are non-parties to UNCLOS, yet the regime it codifies is widely accepted as customary international law.
The International Maritime Organization (IMO), not a political enforcement body, is the primary international institution for maritime safety and shipping standards.

Static Topic Bridges

UNCLOS — The Constitution of the Oceans

The United Nations Convention on the Law of the Sea (UNCLOS), adopted in 1982 and entered into force on November 16, 1994, is the comprehensive international treaty governing all aspects of ocean space. It is often called the "constitution of the oceans."

Adopted: 10 December 1982, at Montego Bay, Jamaica
Entered into force: 16 November 1994
As of 2025, 168 states are parties; notable non-parties include the United States and Iran
UNCLOS defines maritime zones: Territorial Sea (12 nautical miles), Contiguous Zone (24 nm), Exclusive Economic Zone or EEZ (200 nm), and Continental Shelf
India ratified UNCLOS on 29 June 1995
Dispute settlement: UNCLOS Part XV establishes compulsory dispute settlement; the International Tribunal for the Law of the Sea (ITLOS) was established under UNCLOS Annex VI

Connection to this news: Although neither Iran nor the US has ratified UNCLOS, the rules it codifies — particularly on transit passage through international straits — are considered binding customary international law on all states.

Transit Passage vs. Innocent Passage

These two doctrines govern the rights of foreign ships and aircraft through different types of maritime spaces. The distinction is crucial for straits like Hormuz.

Innocent Passage (Articles 17–32, UNCLOS Part II): - Applies to the territorial sea (12 nautical miles) of coastal states - A foreign ship has the right to pass through a coastal state's territorial sea provided passage is "innocent" — not prejudicial to the peace, good order, or security of the coastal state - Submarines must navigate on the surface and show their flag - A coastal state can temporarily suspend innocent passage in specific areas of its territorial sea for security reasons (Article 25(3)) - Aircraft do NOT have the right of innocent passage

Transit Passage (Articles 37–44, UNCLOS Part III): - Applies specifically to straits used for international navigation that connect one part of the high seas/EEZ to another - Transit passage is the freedom of navigation and overflight "solely for the purpose of continuous and expeditious transit" - Coastal states may NOT suspend transit passage for any reason (Article 44) — this is a stronger right than innocent passage - Submarines may transit submerged - Aircraft also enjoy the right of overflight - Coastal states can only regulate matters like safety, pollution, and traffic separation schemes — they cannot levy charges on passage (Article 26 UNCLOS)

Connection to this news: The Strait of Hormuz qualifies as a strait used for international navigation — it connects the Persian Gulf (an arm of the high seas/EEZ) to the Gulf of Oman and the Indian Ocean. This makes it subject to transit passage, not merely innocent passage — meaning Iran cannot lawfully suspend or restrict transit.

The Strait of Hormuz — Strategic and Legal Profile

The Strait of Hormuz is a narrow waterway between the Persian Gulf and the Gulf of Oman, bordered by Iran to the north and Oman (and the UAE) to the south. It is the world's most critical oil transit chokepoint.

Width at narrowest point: approximately 33 km (21 miles)
Approximately 20–21 million barrels of oil transit daily (roughly 20% of global oil consumption and 30% of global LNG trade)
Iran's territorial sea extends 12 nautical miles into the Strait, as does Oman's — together they cover the full width, leaving no high-seas corridor
Iran is not a party to UNCLOS; it argues that general international law gives it broader rights over the Strait
Iran contends the Strait is governed by bilateral treaties and its own 1982 Maritime Zones Act, which asserts tighter controls
The US Freedom of Navigation Operations (FONOPS) programme regularly transits the Strait to contest excessive maritime claims

Connection to this news: Because there is no natural high-seas passage through the Strait of Hormuz — the entire width falls within the territorial waters of Iran and Oman — transit passage doctrine is the only legal mechanism that guarantees unimpeded access for all states.

International Maritime Organization (IMO)

The IMO is a specialised agency of the United Nations responsible for the safety and security of shipping and the prevention of marine and atmospheric pollution by ships.

Established: 1948 (became operational 1959); headquartered in London
India has been a member since 1959; elected to the IMO Council multiple times
IMO does not have enforcement powers — it sets standards, and states incorporate them into domestic law
Key IMO instruments: SOLAS (Safety of Life at Sea), MARPOL (marine pollution), STCW (crew standards)
IMO designates Traffic Separation Schemes (TSS) in congested straits, including the Strait of Hormuz
Political disputes over access and sovereignty are outside IMO's mandate; such matters go to ITLOS or the International Court of Justice (ICJ)

Connection to this news: The IMO's Traffic Separation Scheme for the Strait of Hormuz governs shipping lanes inside the Strait, but the IMO cannot resolve the underlying legal dispute between states over who has the right to restrict transit.

Key Facts & Data

UNCLOS adopted: 10 December 1982; entered into force: 16 November 1994
Non-parties to UNCLOS: USA, Iran (among others)
India ratified UNCLOS: 29 June 1995
Territorial Sea limit under UNCLOS: 12 nautical miles
EEZ limit: 200 nautical miles
Transit passage rule: Article 38 UNCLOS — cannot be suspended (Article 44)
Prohibition on charges for passage: Article 26 UNCLOS
Strait of Hormuz width (narrowest): ~33 km
Oil transit through Strait: ~20–21 million barrels per day (~20% of global oil supply)
ITLOS: Established under UNCLOS Annex VI; seated in Hamburg, Germany
IMO headquarters: London, UK; established 1948
UNCLOS parties: 168 states (as of 2025)