Recently I wrote something that alluded to Tony Blair and war crimes. Apparently, some people thought I was being a bit silly; others that I was naive, impertinent, insulting, or merely provocative. As it happens, there is something to be said for each of those opinions.

Mr Blair will never face any sort of trial over Iraq: that would be the silly part. Such things do not happen to British prime ministers. These days, even impeachment is unthinkable, for better or worse. The western democracies insulate their leaders from such possibilities. There is no accident in that.

Equally, if Mr Blair conducted himself according to the dictates of his conscience throughout the Iraq affair, as he continues to insist, insults and impertinence might sound callow. Errors are not equivalent to bad faith. If the then prime minister also acted from the sincere assumption that edited intelligence reports could always be trusted, the case for his defence could begin to seem credible, morally at least.

The trouble is that none of this has anything to do with war crimes. There is a ton of legal argument on that subject, obviously, but the basic criteria can be put crudely. When is war justified? The first justification is banal: if you are under attack. Secondly, you can fight legally if there is clear, demonstrable evidence that an attack upon you is in preparation. Thirdly, you can wage war if you have received the explicit support of the United Nations. Anything else is unlawful.

Hence, perhaps, the unusual spectacle of fully nine Law Lords gathering to hear the appeal lodged by Rose Gentle and Beverley Clarke. It will take some smart legal thinking to extricate the government, and Mr Blair's reputation, one suspects, from this one. The bereaved pair's lawyers argue that soldiers, given their unique relationship with the state, have a right to know that the cause in which they are ordered to fight is lawful. Mr Blair, they say, did not perform that duty of care.

This week the law lords heard that the then chief of the defence staff was sceptical as to the legality of the Iraq operation. The Treasury solicitor was also unconvinced. Allegedly, lawyers at the Foreign and Commonwealth Office offered the opinion that a second, authoritative UN resolution was essential. "Reasonable steps" to answer these doubts, and to spare the forces' participation in an illegal war, were not taken. Such is the claim.

Memories grow hazy. Too few people now remember, for example, that, pre-war, Mr Blair stood in the chamber of the House of Commons and insisted that regime change in Iraq was not a British ambition. We desired only the impossible: the surrender of non-existent WMD. These days, however, the eradication of Saddam's regime, if not the dictator's execution (another legal conundrum), is held up in some quarters as the moral justification for any mistakes Mr Blair may have made.

Perhaps it is. Blair and Saddam are not interchangeable. The calculus of comparative death tolls does not amount to an argument. We forget, too, that the first "coalition" assault on Afghanistan in the aftermath of 9/11 had widespread and justifiable support, in contrast to the present expenditure of lives to bolster the latest domino theory of geopolitics. "We are all Americans now," as even the French press observed on 9/12. Hunting down Osama bin Laden was the only decent response to a massacre, and accepted as such.

Accepted as such by this columnist, certainly. Nevertheless, America has still to puzzle out why so much goodwill was then squandered so easily, so quickly, so casually after 9/11. Even the naive among us should have guessed. Offered Iraq, tied up in ribbons of lies while the search for bin Laden was forgotten, we remembered our history. The self-appointed forces of righteousness commit war crimes, too. And even pretty straight guys will tell you a bare-faced lie while summoning the 2973 dead of the Twin Towers.

The mothers of two dead 19-year-olds have given nine law lords pause for thought, or so I hope. My guess, though, is that a great deal of legalese will attach itself to the word "reasonable", and that the concept of a war crime will be lost in the whisper of ermine. A pity. But if the London government is confident that it can escape one humiliation - what is a law lord for, after all? - it still has its moral standing to consider, Blair or no Blair.

I'm being naive again. David Miliband, the latest Foreign Secretary, has been telling us that the "mistakes" of Iraq and Afghanistan should not deter Britain from the moral imperative of interventionism, that we should stand ready to participate, militarily if need be, in efforts to aid democracy. Gall acquires its own peculiar credibility. Does Mr Miliband have a particular war in mind for our overwhelmed armed forces, or has someone supplied him with a dossier?

In a speech at Oxford yesterday, the Foreign Secretary invoked a "moral impulse" in overseas policy. Robin Cook took that approach, once upon a time, and found himself resigning when the truth dawned. Undaunted, Mr Miliband is keen on the "forward march of democracy". In which direction will he march, then, when America strings up half a dozen Guantanamo detainees?

It comes under the heading, I think, of a "moral duty to intervene". The United States is the only Nato member to continue to practise capital punishment. It is the only half-way civilised state to insist that military tribunals have anything to do with democracy. And it is the only extant democracy that excuses - or rather, does not lie about - evidence and confessions extracted under torture.

The October surprise has come early in the presidential election cycle. Since John McCain is a candidate content to see US forces occupying Iraq and Afghanistan for "a century", it will do him no harm to have the spectre of terrorism and 9/11 raised again. He has already enjoyed the clammy Bush embrace - Republican hypocrisy approaches an art form - but that is of little help to Mr Miliband and his government.

The Pentagon is requesting the death penalty for six "high value" al Qaeda suspects, including that of Khalid Sheikh Mohammed, one of numerous individuals ranked third in bin Laden's group, and a man "waterboarded" (near-drowned) by his captors. Does Britain have no view on summary execution? On torture? On legal process?

There are 169 charges against six men. The chances are that condign punishment is richly deserved. Since I am not foreign secretary, however, and since I do not place a special value (quite the opposite) on a special relationship, I can ask the dumb question. If six fanatics seek martyrdom, and if martyrdom is the last propaganda service they can offer their cult, do you oblige?

Do you advertise democracy by denying access to lawyers? Do you deny prisoner-of-war status thanks to specious legalisms that do not, in fact, impress your own Supreme Court? Do you hold up eventual access to that court as a mark of due process when the world knows that this minimum condition was imposed on the Pentagon and the White House, kicking and screaming, by the justices?

For our purposes, ask only this: why should Britain associate itself with any of this? This is the real moral dimension. This is, strangely parallel, the truth Rose Gentle asks us to recognise. I'm still naive: we are supposed to be better.