Naval Blockade in International Law
A naval blockade is a belligerent act under international law that restricts the movement of ships to and from an enemy's ports or coast. Under UNCLOS (United Nations Convention on the Law of the Sea), straits used for international navigation enjoy a right of "transit passage" — all ships and aircraft have the right to pass through in continuous and expeditious transit. Blockading a strait used for international navigation is therefore legally contentious and politically explosive.
- UNCLOS Article 38 guarantees the right of transit passage through straits used for international navigation.
- The US framed its blockade narrowly as intercepting only Iranian port-bound vessels while claiming it maintained general freedom of navigation for others.
- Iran characterised any US naval presence limiting its own shipping as a blockade, triggering its own counterthreats.
- A blockade by one state that impedes neutral third-party shipping may be considered a violation of the freedom of navigation principle under customary international law.
● Tracked since April 18, 2026 · last seen April 18, 2026 · updates as the daily brief publishes
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