WHILE Britain was probably within its legal rights to seize the Iranian tanker Grace 1 off Gibraltar, Tehran’s retaliatory act of detaining the UK-registered Stena Impero in the Strait of Hormuz is rather less clear, according to maritime law experts.

Foreign secretary Jeremy Hunt accused Iran of ‘state piracy’, while Tehran has thrown similar insults back at London. However, the designation is inaccurate, at least from a legal rather than a rhetorical point of view.

While both seizures were politically driven, the UK appears to have a stronger argument, in that a vessel allegedly in contravention of EU sanctions was passing through the territorial waters of a British Overseas Territory.

Iran has attempted to justify last Friday’s capture of Stena Impero by claiming that it had been in collision with a fishing vessel, albeit outside Iranian waters. However, the facts of the matter have not been verified independently.

Coastal states have two potential frameworks that give them the legal power to seize a vessel owned by, or flying the flag of, another state, according to Nick Barber of Stephenson Harwood.

These are the state’s own laws and the United Nations Convention on the Law of the Sea 1982 (UNCLOS), which has a sufficiently wide acceptance to be considered customary international law, and therefore binding even on states which are not signatories. Iran has not ratified the convention.

The law of the state in question extends to whatever limit the country specifies. UNCLOS extends to the limit of its territorial sea, generally 12 nautical miles out from a state’s coast.

“A state has sovereign jurisdiction to exercise its own laws within its territorial sea, so on the face of it, if a state says it is legal to seize a vessel, it is legal,” said Mr Barber.

States also have some jurisdiction beyond the territorial sea, but there are caveats.

UNCLOS provides that ships of all states enjoy the right of innocent passage through the territorial sea, or transit passage through a strait used for international navigation. Seizure of a vessel which is enjoying these rights would be unlawful as a matter of international law.

But under it, states can adopt laws and regulations relating to innocent passage or transit passage, primarily with regard to issues such as the safety of navigation, protection of living resources and protection of the environment.

The rights of states to seize vessels on the high seas are extremely limited, Mr Barber added, although they do include the right of ‘hot pursuit’, where an infringing vessel is chased without interruption, from within a coastal state’s Exclusive Economic Zone to the high seas.

However, the UN convention provides that piracy is an act committed for private ends by the crew or passengers of a private ship or aircraft, so state seizure cannot constitute piracy within the internationally accepted definition of the word.

Charles Buss, a partner at WFW, said that in general, coastal states have the power to seize ships when crimes are committed under domestic laws, or if assistance has been requested by the master, or such a step is required for the suppression of trafficking in narcotic drugs.

“These cases often come before the English courts, because people make claims under their war risks policies for their losses. Then the legality of the detention gets argued out,” he said.

He highlighted a case in which the Egyptian authorities seized a vessel, ostensibly to obtain security for pollution liabilities. But the English courts ruled that this was `seizure unlawful'.

“In theory, the Iranian detention could be legal. But on the facts, it would probably be regarded as illegal,” he said. “We have a fig leaf. Our government can say we were right, legally speaking, because we were applying the law, subject to there being any uncertainty that Grace 1 was bound for Syria.

“It was breaching EU sanctions, and we were able to detain it in territorial waters, whereas the Iranians diverted a ship from international waters.”

Even so, the Iranian action cannot be considered piracy, a term that a.101 of UNCLOS restricts to acts committed by crew or passengers of one private ship against another ship for private ends.

In so far as Iran’s Revolutionary Guards are functionaries of the Iranian state, they cannot be said to have detained Stena Impero for private ends.

Meanwhile, marine insurer Hiscox has launched a new product, which will cover owners against the risk of what it has dubbed Malicious Vessel Seizure.

The policy will respond to a single peril of a ship taken by a foreign government, providing loss of hire costs and the services of leading crisis management consultancy Control Risks.

Control Risks will help the owner or charterer with crisis management support, including government liaison and family support for the victims

However, no ships trading with Iran will be considered, Hiscox said in a statement on its website.