Action taken by the island nation of São Tomé and Príncipe following a dispute about a Maltese-registered vessel was disproportionate considering the original offence, an international tribunal has ruled.

The dispute concerned the Maltese-registered Duzgit Integrity, which ran into trouble with authorities in São Tomé and Príncipe after attempting to undertake a ship-to-ship cargo transfer in the country's archipelagic waters.

Transport Malta said in a statement today that on October 22, 2013, Malta instituted arbitral proceedings against São Tomé and Príncipe.

An international tribunal at the Permanant Court of Arbitration at The Hague has now unanimously found that it had jurisdiction over the dispute and that Malta’s claims were admissible.

In its decision, the tribunal noted that, under international law, enforcement measures taken by a coastal state in response to activity within its archipelagic waters were subject to the requirement of reasonableness, which encompassed the general principles of necessity and proportionality.

It found that the initial measures taken by São Tomé and Príncipe fell within the exercise of its law enforcement jurisdiction.

However, it also found that the other penalties imposed by São Tomé and Príncipe – the prolonged detention of the master and vessel, the monetary sanctions, and the confiscation of the entire cargo – when considered together, could not be regarded as proportional.

It found that the disproportionality was such that it rendered the cumulative effect of the sanctions incompatible with the responsibilities of a state exercising sovereignty and held that Malta was entitled to claim reparation regarding certain heads of claim in a later phase of the arbitration.

Transport Malta said this case has highlighted the Maltese government’s commitment to afford the necessary support to operators operating their ships under the Maltese flag.