Ruling to release vessel that was commandeered by UK came despite last-minute US attempt to detain it.

Gibraltar’s Supreme Court has ruled that a seized Iranian oil tanker is free to sail, just hours after the United States made a last-minute attempt to keep the vessel under detention, authorities said.

Grace 1 had been commandeered by the British Royal Marines off the coast of Gibraltar on July 4 on suspicion it was carrying Iranian crude oil to Syria in breach of European Union sanctions against the government of Syrian President Bashar al-Assad.

Iran had denied the accusation and called the seizure “an act of piracy” committed at the behest of the US.

The tanker, which remained docked off the coast of the British territory off Spain’s southern coast into Thursday evening, has since become a pawn in the escalating tensions between Iran and the US.

The Gibraltar government on Thursday reiterated its conviction that the ship had been bound for Syria with $140m worth of light crude oil on board, in violation of separate EU and US sanctions. The boat’s navigation plan “showed a fully marked-out route” from the Gulf to the Syrian port of Baniyas, the government said.

Gibraltar Chief Minister Fabian Picardo said he had met Iranian officials on July 19 in London “with a will for a de-escalation with regard to all the various problems arising from the detention of the Grace 1”.

The Supreme Court decision to release the tanker came on Thursday after Iran guaranteed in writing that the Grace 1 would not be heading to countries “subject to European Union sanctions” once it left the port, and therefore the ship was “no longer subject to detention”, Chief Justice Anthony Dudley said.

Later on Thursday, the United Kingdom‘s Foreign Office called on Iran to stand by its pledge that the ship would not sail for Syria.

Gibraltar officials said a last-minute appeal from the US to extend the detention was not considered an official request before the Supreme Court, so they went ahead with the release.

“As far as the judge here is concerned at the Supreme Court, the Grace 1 is free to leave right now,” Al Jazeera’s Andrew Simmons, reporting from Gibraltar, said.

Possible swap

The ruling came after a day of confusion surrounding the tanker, with the government in Gibraltar saying plans to release the vessel had been delayed by the last-minute request from the US Department of Justice to extend its detention.

The US request will be reviewed by the territory’s Independent Mutual Legal Assistance authority, which can decide whether a separate court case can take place, Picardo told reporters. If the review were to happen before Grace 1 left Gibraltar’s waters, the detention could still be extended.

It was not immediately clear if there was a crew willing and able to man the ship, but Iran’s ambassador to Britain, Hamid Baeidinejad, tweeted after the court ruling that the ship would “soon leave Gibraltar”.

The captain of Grace 1 and three officers had been released from detention in preparation for the vessel’s release [Jon Nazca/Reuters]

It also remained unclear if the decision would prompt Iran to release the British-flagged Stena Impero, which the Islamic Republic had seized in the Strait of Hormuz on July 19. At the time, Iran said the vessel had collided with a fishing boat and violated international law, but later Iranian President Hassan Rouhani appeared to suggest that if the UK released Grace 1, then his country would return Stena Impero.

A spokesman for the Stena Impero’s owner said after the ruling that the situation remained unchanged and that the company awaited further developments from the UK and Iran.

“Now this is a way for both sides to defuse the situation and save face,” Al Jazeera’s Assed Baig, reporting from Tehran, said.

In its statement, the UK foreign office denied that there had been any link “between Iran’s unacceptable and illegal seizure of, and attacks on, commercial shipping vessels in the Strait of Hormuz and the enforcement of EU Syria sanctions by the Government of Gibraltar.”

Escalating tensions

The US and Iran have traded barbs and accusations as tensions have risen over the Strait of Hormuz, a narrow waterway between Oman and Iran through which a fifth of the world’s oil is transported.

Since May, the US has repeatedly accused Iran of sabotaging tankers in the strait, an accusation Iran has denied.

In June, Iran downed a US military surveillance drone in the Gulf with a surface-to-air missile. Tehran said the drone was in its airspace, while Washington said it was in international skies.

The US military has since deployed additional forces, including an aircraft carrier and B-52 bombers, to the Middle East as tensions have mounted. It also began a joint naval mission in the region with the UK, who were prompted to join by the seizure of the Stena Impero.

On Thursday, Iran’s Foreign Minister Mohammad Javad Zarif derided Washington’s last-minute attempt to seize the tanker, accusing the US of trying to “steal our property on the high seas”.

“Having failed to accomplish its objectives through its #EconomicTerrorism – including depriving cancer patients of medicine – the US attempted to abuse the legal system to steal our property on the high seas,” Zarif tweeted on Thursday, referring to US sanctions that Iranian officials say have prevented cancer patients from receiving medicines.

He added: “This piracy attempt is indicative of Trump (administration’s) contempt for the law.”

In preparations for the tanker’s release, the captain of Grace 1, an Indian national, and three officers had been released from detention on Thursday, the Gibraltar government said.