The Legal Foundation of Maritime Freedom

The Strait of Hormuz is not just a geographic and strategic landmark — it is also a focal point for some of the most important and contested questions in international maritime law. The primary legal framework governing passage through the Strait is the United Nations Convention on the Law of the Sea (UNCLOS), which entered into force in 1994 and has been ratified by the vast majority of the world's nations.

Understanding what UNCLOS says — and where the disagreements lie — is essential for understanding why the Strait's legal status remains a source of ongoing tension.

What Is Transit Passage?

UNCLOS establishes several different regimes for passage through different types of maritime zones. The most relevant for the Strait of Hormuz is transit passage, which applies to straits used for international navigation between one part of the high seas (or an Exclusive Economic Zone) and another.

Under UNCLOS Part III (Articles 37–44), transit passage grants ships and aircraft the right of continuous and expeditious passage through or over such straits. Key provisions include:

  • Ships may transit in their normal mode of operation — meaning submarines may transit submerged, and warships may transit without prior notification or permission.
  • Aircraft, including military aircraft, have overflight rights in transit passage straits.
  • Coastal states bordering the strait may not suspend transit passage for any reason.
  • Coastal states may designate sea lanes and prescribe traffic separation schemes, subject to IMO approval.

This regime is significantly more permissive than "innocent passage," which requires surface navigation and allows coastal states more control over who passes through their territorial seas.

Iran's Position: A Challenge to the Consensus

Iran ratified UNCLOS but has consistently taken legal positions that differ from the mainstream Western interpretation. Iran argues that:

  • Warships of non-coastal states require prior authorisation to transit Iranian territorial waters.
  • The transit passage regime should not automatically apply to military vessels in a manner that overrides coastal state security interests.
  • Foreign military exercises and intelligence-gathering activities in the Strait are not covered by transit passage rights.

These positions are not accepted by the United States, the United Kingdom, or most other major naval powers, who maintain that UNCLOS's transit passage provisions apply fully to the Strait of Hormuz and that no prior permission is required for any type of vessel.

The Breadth of the Strait and Territorial Waters

One important legal characteristic of the Strait of Hormuz is that it is narrow enough that both Iran's and Oman's 12-nautical-mile territorial sea claims overlap — meaning there is no strip of high seas in the middle of the Strait where vessels could transit outside territorial waters entirely. The entire navigable channel lies within territorial sea claims.

This makes the transit passage regime critical: without it, every vessel would be subject to the more restrictive innocent passage rules of coastal state territorial seas, giving Iran and Oman far greater legal authority over transiting ships. The transit passage regime was specifically designed to prevent this outcome for strategically important straits.

The Abu Musa and Tunbs Dispute

Overlapping with the navigation law questions is a sovereignty dispute over three islands in the Strait: Abu Musa, Greater Tunb, and Lesser Tunb. Iran seized these islands from the UAE (then the Trucial States) in 1971. The UAE has never recognised Iran's sovereignty over them and continues to claim them.

The dispute is not merely symbolic. Control over these islands gives Iran military and surveillance positions within the Strait itself, affecting both the security and legal picture. The UAE regularly raises the issue in Arab League forums, while Iran considers the matter settled.

Freedom of Navigation Operations (FONOPs)

The United States conducts Freedom of Navigation Operations (FONOPs) globally to challenge what it considers excessive maritime claims. In the Persian Gulf region, US naval vessels and aircraft have consistently exercised transit passage rights in ways that challenge Iranian claims — transiting without notification, conducting submarine operations, and flying military aircraft over the Strait.

These operations are deliberately calibrated to maintain the legal precedent that UNCLOS's transit passage regime applies fully to the Strait of Hormuz and that no coastal state has the authority to restrict it for political reasons.

The Enduring Legal Tension

The legal framework governing the Strait of Hormuz is well-established in international consensus, but Iran's dissenting interpretation means the underlying tensions are unlikely to be resolved by legal argument alone. In practice, the regime of transit passage continues to operate — thousands of vessels transit annually without incident — but the legal disagreement remains a potential tool that could be invoked during any future escalation.