We went in even though the evidence suggested he didn't have them; we won't go in when everyone's pretty sure he does. The relationship between British military intervention and dictators and their chemical weapons is laden with irony. The spectre of Iraq and Whitehall's inability to disentangle truth from wishful thinking looms over the contemporary tragedy of Syria.

President Bashar al-Assad is likely to have calculated that he can get away with gassing his civilian population, because of what happened a decade ago with Saddam Hussein and his elusive weapons of mass destruction.

Nobody who has watched the footage from the Damascus suburb of Ghouta – the row upon row of dead bodies, the babies writhing in agony – can fail to have been horrified and galvanised. After being almost surrounded by rebels a year or so ago, Assad has seemingly deployed all weaponry at his disposal to annihilate the threat. He has been able to do so because the international community has been high on rhetoric and low on action.

The impotence of now recalls the blind eye the UN turned towards Rwanda and Bosnia in the 1990s; this in turn fuelled the full-blooded interventionist zeal of Blair and Bush. So has the world turned full circle? The answer is "no", whatever action may eventually be taken against Syria.

Iraq is part of the reason, but only part. It was salutary to hear the solemn tones of former UN weapons inspector Hans Blix talking last week about inspections, delays and cover-ups. The refusal of the Americans and British to allow Blix to finish his work in 2002-3 continues to undermine any accusations based on assertion alone, no matter how credible those assertions might be today. And now that Assad appears to have agreed to UN inspections of the gas attack site, it will be a race against time to sift through the evidence.

However, though it might sound a little arcane to raise the issue, with thousands of victims of Assad's likely use of nerve gas, it still beggars belief that the British establishment continues to give the impression of wanting to hide the mistakes and falsehoods on Iraq. Where, one might reasonably ask, is that elusive Chilcot report? The refusal to publish it, until all those involved are a distant memory, reinforces the view that the spooks and the politicians do not want the full truth to come out.

This matters in terms of the barbarism of Ghouta because it is only after a full reckoning on Iraq that Britain can, with a clear head, grapple with the ongoing question of human rights abuses and military intervention.

Irrespective of the domestic pressures, the balance of forces has shifted in the intervening 10 years. The United States has a president, a body politic and public opinion scarred by Iraq and Afghanistan and largely averse to the use of military force. The Franco-British air strikes on Libya straddled the old ways and the new realities. Prompted by the potential for a massacre in Benghazi, David Cameron and Nicolas Sarkozy were alive to the consequences of doing nothing. But the mission succeeded (in its initial aims) only because of American logistical support and Russian acquiescence at the UN.

Later, the Russians cried foul, arguing that the UN mandate did not allow the west to topple Gaddafi. Their intransigence towards Syria partly reflects their strategic alliance with Assad, but also their fury (rightly or wrongly) over Libya.

They have been doling out the revenge ever since, and Syria is the perfect forum for them. With the support of China, Russia ensured last week that even a resolution mandating a full inspection of the chemical attack in Damascus was watered down to the point of absurdity.

It may have been relatively easy in the 1990s for the British and Americans to act without UN endorsement, with China only beginning to emerge as a potential superpower and Russia led by an alcohol-infused Boris Yeltsin. Now the risk of ignoring them is far greater, although it may be a risk the US and UK are prepared to take.

Cameron, to his credit, has formalised the process of war. Gone are Blair's sofas, and diplomats and military required to tailor their operations to the exigencies of spin. But the dilemmas remain unresolved. Without formal UN support, what is the legal basis for action? What are the goals and are they achievable? To scare Assad? He won't be. To punish or remove him? The Russians will amorally ensure he clings to power.

The more honest admission would be that military action in Syria is a response to an instinct that something must be done, that the tyrant can't get away with it. That might be an understandable moral reflex, but it does not make for long-term policy.

The fear is that, after a brief flirtation, the world is turning away from a rights-based approach. I hope I am wrong, but Assad may be smiling, knowing that, even if we hit back at him in a token gesture over the next few weeks or months, he could be around for quite some time.