When Frontex started, haltingly, four years ago, it was presented as an essential guardian in discouraging the huge surge of illegal immigration across the central Mediterranean, stemming mainly from Libya. Malta was a keen supporter of this initiative.

A crucial prerequisite to the success of Frontex operations was always hoped to be the cooperation of Libya. Ideally, in order to act as a serious disincentive to illegal immigrants, Frontex operations were to be carried out jointly with the Libyan authorities and as close to the known Libyan ports of illegal immigrant embarkation as possible. That operational scenario never got off the ground. Tripoli refused to cooperate and the European Union was reluctant to press the issue.

While Frontex would claim that the presence of their maritime and air military assets in the central Mediterranean helped to deter many would-be illegal immigrants from using that particular route into Europe, the evidence to support this is scanty. Certainly, it failed to turn back or dissuade the almost 3,000 illegal immigrants who reached Malta in 2008. Frontex would further insist that the position would have been far worse without their presence. It is difficult to prove a negative.

What everyone certainly knows is that the drop in numbers in 2009 - compared to the year before - owed more to a sudden agreement by Libya, probably under pressure from Italy, to take back illegal immigrants picked up at sea and proven to have departed from its shores. This cooperation has persisted to date but could change overnight.

The jury is, therefore, still out on whether Frontex is a cost-effective operation or merely a fig-leaf for gesture politics by the EU. The truth is that, from its inception, political feelings within the EU about Frontex's efficacy and the way it should operate were mixed. The north-south divide within Europe, which still colours how illegal immigration in the Mediterranean is viewed, affected not only what military assets nations were prepared to devote to it - these have been meagre and the Armed Forces of Malta have indeed provided the bulk - but also what its operational "rules of engagement" or guidelines should be.

This issue has now come to a head over the matter of what to do about illegal immigrants picked up outside Malta's search and rescue region (SAR) and inside Libya's. The proposed guidelines, as drafted, lay down that if it is not possible to return migrants picked up by Frontex vessels to the country from which they had departed, then they must be accepted by the country hosting the Frontex mission. And this follows so much talk and posturing within the EU about how essential it is to help tiny Malta in its predicament.

Malta and Italy have rightly rejected this proposal and have expressed reluctance to host or even take part in any missions under this arrangement.

Malta is absolutely correct to reject any deviation from international maritime law, which stipulates that anybody rescued in distress on the high seas should be taken to the nearest available port. It would be utterly contrary to this - and impractical as well as contrary to natural justice - if those migrants rescued in Libya's SAR were in future to be taken to Malta simply because the island was host to Frontex and Libya had refused or been unable, for whatever reason, to fulfil its SAR responsibilities.

In such circumstances, better no Frontex operation in this region at all than one that would exacerbate Malta's already precarious immigration problems.