But .....
There are rather a lot of serious concerns about this execution that do need to be addressed. It isn't good for the soul of a politician if he can set himself up as judge, jury and executioner and then receive widespread praise for his actions. It may well be that in this particular case the intelligence received by Cameron and the Americans was rock solid and they identified the right man and he was accompanied by a crowd of other people who also deserved to die. We know that the intelligence that came out of Iraq about weapons of mass destruction was flawed and came from sources that were biased but thought to be objective and honest. Let us hope that on this occasion things were very different and they got the right people for the right crime.
If they did then what next? Let us suppose that this sets a precedent. If the Prime Minister of the UK or the President of the US thinks there is clear evidence that a British murderer is at large in a war zone then they have the power to order them to be killed. What are the limits to that right? How does the PM determine which crimes and how many crimes are big enough to justify judicial killing abroad? How does the PM determine when there is sufficient evidence that the crime is bad enough to justify the death penalty. How does the PM judge whether the person he has ordered to be killed is indeed the guilty party and those with him/her also deserve the same fate? Where do the boundaries stand between crimes the PM can execute someone for and ones that he can't and who decides and how? Does the PM need to consult the Privy Council members and get their views before he acts and does that include Jeremy Corbyn or have we given up on attempts at consensus on matters of this importance?
All of these questions seem to me to lead to very worrying answers. Are we about to witness a moral drift where the PM starts out ordering one execution in circumstances that the vast majority of decent people would understand and then ends up deciding for himself on a regular basis who he wants to get rid of today?
If that doesn't worry you then there is one other question I would suggest is worth thinking about. Does this kind of execution help those who want to achieve a decent peace with security and freedom or does it actually help the so called Islamic State? It removes one nasty piece of work who thoroughly deserves it. That probably makes Cameron feel pretty good about himself for a couple of days and will certainly help him to rise up a long way in the opinion polls. In military terms exactly what does that achieve for those of us who actually want to defeat ISIS? Is it meant to be a deterrent? If so how does that work on people who boast that they are ready for martyrdom?
Now ask the question about the strategic gains and losses from the point of view of the other side. If you are an ISIS propagandist what are the gains and losses of this killing for you? You are down one bitter twisted individual who was high profile and his death might put a few people off from wanting to sign up for the cause. On the other hand you have a martyr for the cause. Just what you always wanted. You have evidence of the US and the UK taking unilateral action on someone else's territory. Just what you always wanted. You can use this killing to construct a narrative of a brave freedom fighter. That will bring you in a great deal of money (a good deal of which will come from countries allied to the UK such as Saudi Arabia) and a lot more recruits than the one you have just lost.
Instead of weakening ISIS Cameron has just strengthened them. As I write I am sure that they will have their own propagandists working away on twitter and facebook trying to convince people that they are the most determined defenders of the true faith. They are not but Cameron has just helped them to adopt that image. Some of their apologists will now be busily engaged in telling us that their is nothing to choose between Cameron and ISIS. There is. There are degrees of morality and shades of difference between people that we disagree with. Beheading an aid worker is at the outer edges of morality. An elected politician recklessly taking the law into his own hands is bad but not remotely in the same league. To talk as if there was a moral equality between torturing and then beheading a completely innocent aid worker and trying to execute a murderer is seriously wrongheaded. We are not dealing with a moral equality between ISIS and Cameron. ISIS really is engaged in systematic genocide against minorities with different faiths. ISIS really is raping young girls to force them to obey extraordinarily cruel men. ISIS really is a form of religious fascism.
Cameron has many faults but he is not a fascist, he doesn't hand women over to his military commanders to do with as they wish and he doesn't impose extra 'taxes' on his opponents and kill them if they can't afford the bribes. I am as opposed to Cameron and his political view as anyone around but morality isn't absolute and there are degrees of horror and in my view ISIS exceeds anything Cameron would even begin to be capable of.
So my objection to Cameron ordering foreign executions is not based on a love of ISIS or some naive conviction that he and ISIS are as bad as each other. They are not. Nor is my objection based on pacifism. There are circumstances where you need to go to war and sometimes you have to do pretty nasty things to win that war as anyone who studies the Second World War will quickly find out.
My objection is based on two simple worries.
1. Cameron hasn't thought hard enough about what happens next. Now that we have started down this route where and when does it end? What would his attitude be if other countries like Russia and China started claiming the same rights to act in what they see as defence of their own citizens?
2. Will this action simply make things worse? Will ISIS win the propaganda war with enough people to make it counterproductive. Has he made a hard headed calculation of military necessity or a cynical calculation of political short term self interest?
Cameron is, I suspect, feeling pretty good with himself today. He is presenting himself as a hard man who is prepared to make difficult decisions to defend his fellow citizens. Perhaps he should sober up on the overdose of machismo for long enough to ask himself a few vital questions for his legacy. Does he really want to become yet another politician who believes his own propaganda. Does he really want to go down in history as someone who got Britain involved in another set of reckless ill thought out actions in other people's countries? Or is one Tony Blair is enough for any country?