But as more information comes to light it appears that the British-owned tanker, Stena Impero, was in breach of international regulations, in addition to posing a threat to the environment in the event of a collision with other vessels in the region, which would have been unaware of its presence due to its transponder having been switched off.
Iran’s legal basis for the detention of the Stena Impero rests primarily on its transgression of laws and regulations pertaining to the United Nations Convention on the Law of the Sea (UNCLS).
According to an official communiqué released by Iranian authorities, the Stena Impero was on a course in contravention of its legitimate direction of travel.
As the British-flagged tanker was not following the correct path it may be considered to be in breach of section 3 of the UNCLS, which relates to the right of innocent passage.
Under article 18 of section 3, ships are entitled to the right of innocent passage as long as their journey is “continuous” and “expeditious”. In the case of the Stena Impero, the vessel is suspected to have deviated from “continuous” passage by changing course.
An additional breach of section 3 (right of innocent passage), this time under article 19, may have occurred due to the Stena Impero’s collision with a fishing trawler, which may, or could have, resulted in oil leaking from the tanker, thus resulting in an environmental disaster, with terrible consequences for the entire region.
Under article 19, section 3, of the UNCLS, passage is innocent as long as it is not prejudicial to the “peace, good order or security” of the coastal state.
Moreover, the Stena Impero could be regarded as posing a security threat on account of the fact that it had gone “dark”, meaning its transponder was switched off.
Based on these established and emergent facts it would appear that far from being a tit for tat response, the Iranian decision to detain the British vessel was in conformance with the Islamic Republic of Iran’s obligation to uphold laws and norms pertaining to navigation on the high seas.