The killing of Osama bin Laden is an instance of a much more general policy pursued by the United States and its allies – the targeted killing of named individuals in the war against terrorism and against various insurgencies in Iraq and Afghanistan. In the midst of American celebration of the fact that al-Qaida has lost its charismatic leader, it is worth getting clear about targeted killing in general, i.e. about the legality and the desirability of a policy of this kind. Targeted killings are of two kinds. The first involves killing people who are actually engaged in carrying out terrorist acts – planting a bomb or preparing someone for a suicide bombing. The second involves the elimination of high-profile individuals whose names appear on a special list of active commanders and participants in terrorism or insurgency. These killings are part of a strategy of disruption and decapitation directed against terrorist organisations.

Killings of either kind can be problematic from a legal point of view (the more so if they involve the violation of another country’s sovereignty). But they may be lawful depending on the circumstances. What is certainly forbidden is targeted killing for the sake of justice or vengeance, both of which have been cited by American authorities as justifications in this case. Calling the killing of Osama bin Laden ‘justice’ summons up very primitive notions of retribution, utterly dislocated from the rule-of-law processes that the civilised world prides itself on. If justice in the strict sense had really been in question, an attempt would have to have been made to capture the man alive. Despite some initial equivocation, it is plain that no such attempt was contemplated.

I think the only possible justification for the shooting of bin Laden was as a legitimate act of war. A White House spokesman has said the killing was a legitimate act of self-defence. I assume this wasn’t intended as an analogy with self-defence as that term is understood in criminal law, for we do not allow the shooting of people in their beds on the grounds that they have been dangerous in the past or may be in the future. Nothing but an immediate threat, an imminent threat, will do. Talk of national self-defence can only refer to the conduct of defensive war under the auspices of Article 51 of the United Nations Charter. That is where the justificatory debate should be focused.

Many people – most prominently the Archbishop of Canterbury – have said that the bin Laden killing leaves them with ‘a very uncomfortable feeling’. Here are some questions designed to identify possible sources for this discomfort.

First, are we happy to have the principle on which this killing was conducted made available in the world for use by any government against those it can plausibly describe as threats to its security or its national interest? Think of Russia in the Caucasus or China in its restive western provinces.

Second, who would have been a likely target if a policy like this had been adopted by Britain or by any number of countries against other kinds of enemy in (say) the last 50 years. We defend targeted killing when the targets are terrorists, but the term ‘terrorist’ was used almost reflexively by colonial or repressive governments to apply to insurgents or enemies of the regime. South Africa called Nelson Mandela a terrorist and attempted the targeted assassination of various members of the ANC including Albie Sachs (who later sat, maimed by the attempt, on the South African Supreme Court). For that matter, think of the British government’s fondness for describing virtually every active opponent against colonial rule in the 1950s and 1960s as a terrorist, including many who later became respected statesmen. Or think of the harm that might have been done to peace prospects in Northern Ireland if a shoot-to-kill policy had been used more widely against IRA commanders than in fact it was. Sometimes one has to refrain from ‘decapitating’ an organisation so that there is somebody left to talk to.

People may say it is wrong to condemn a practice simply on the grounds that it might be abused (or on the ground that it has been abused in the past). But everything depends on how we propose to guard against abuses. Governments tend to lie reflexively when killings of this kind come to light, and both the British and the American government long ago squandered the trust that would be necessary to assure us that the power to mobilise death squads – units specially trained for targeted killing – will not be abused.

It is sometimes said that hard cases make bad law. The same might be said about cases where the justification is reasonably clear. Osama bin Laden was at the head of an organisation that posed a deadly threat and, as I said, his killing is probably justified as an act of defensive war. But preoccupation with the striking facts of this case – and the special feelings of exhilaration it seems to have engendered – should not blind us to the dangers and temptations of targeted killing in general.

In politics and the pursuit of national security, the stakes sometimes seem very high. The viability of national policy may be at stake, or innocent lives, or the survival in office of not so innocent politicians. And it may sometimes seem that it would be easier simply to ‘eliminate’ some of those who are leading the insurgency – posing this threat to the life of the nation – than to continue risking the values that the government stands for. Certainly that might seem easier than what can be achieved through the uncertain and drawn-out procedures of ordinary law enforcement and less costly (from a political point of view) than what can be purchased in the uncertain currency of negotiation and the addressing of grievances. Assassinating those who can be designated plausibly as ‘enemies of society’ has always been one of the standing temptations of government. It would be unfortunate if this killing meant that we were embarking now on a phase of national security policy in which death squads were preferred to political solutions or conventional law-enforcement.