Leading Article: A no-fly zone proves itself . . .

PERHAPS President Saddam Hussein of Iraq was anxious to remind the world that he remains in power even as his old adversary President George Bush prepares to bow out. Whatever the prime motive, the episode in which one of his valuable MiG fighters was shot down by a US warplane over Iraq's southern no-fly zone is confirmation of the value of allied restraints on his sovereignty.

It is unlikely that the incursion by the two Iraqi fighters, one of which was shot down, was an accident or an unauthorised initiative by a local commander - not least since it followed a similar but briefer move only 20 minutes earlier. Most probably it was blessed by President Saddam himself, with the aim of testing American resolve and perhaps of elucidating the level of President-elect Bill Clinton's commitment to the policy of the Bush administration.

Whatever the purpose, the effect is clear. Saddam Hussein has shown how bitterly he continues to resent the no-fly zones imposed last August over Iraq south of the 32nd parallel, and over the Kurdish region north of the 36th parallel at the end of the Gulf war. The Americans have shown that they remain vigilant on behalf of the dissident Shias and marsh Arabs of southern Iraq, for whose protection from bombing and helicopter attacks the no-fly zone was belatedly imposed.

The episode will have done these long-suffering peoples a service if it renews concern for their plight. Inquiries on behalf of Amnesty International in November indicated that President Saddam's army was continuing its relentless bombardment of their strongholds, and that there has been a campaign of mass arrests across the Shia south. Parts of the marshes were being drained, ostensibly for irrigation purposes, thus destroying centuries-old patterns of life and reducing the area of relative safety. In short, President Saddam seems as determined to liquidate his enemies there as in the north where, thanks to the allies, they are protected and largely autonomous. Only a week ago he promised that 'peace and security' (of his own murderous brand) would be re-established in northern Iraq once Western elements were 'kicked out'.

There are those who question the legality of the two no-fly zones, which were declared by Britain, France and the United States as permanent members of the UN Security Council without a general vote being taken. The Americans argue that authority to protect persecuted groups in Iraq derives from Security Council Resolution 688, which demands that Iraq halt such repression. The French and British see a new principle of international law emerging, allowing military intervention to prevent a humanitarian catastrophe. In that case, their critics ask, why bother to seek a vote first on intervention in Somalia, and now on the enforcement of the proposed no-fly zone in Bosnia?

The answer is clear: for new applications of new principles, maximum consensus is politically desirable. As the incident in the skies above southern Iraq has reminded us, President Saddam remains a menace to the stability of the Middle East and to those of his own people brave enough to challenge his cruel autocracy. The allied commitment to keep his warplanes from the skies must be sustained until their security is guaranteed by other means.