If I hear another anti-war protester or commentator use the word “illegal” to describe the war in Iraq, I will throttle them.

Not because I think the war was “legal”, or because I supported the war; in fact I was an implacable opponent of invading Iraq since long before the invasion took place. Rather, I despise the cries of “illegality” because implicit in this line of attack is the idea that if the war had been legal – had the UN security council decided in its infinite wisdom that Saddam really was tooled up with WMD and thus deserved a whooping from the west – then the invasion and destruction of Iraq would have been OK, or at least better. In fact, there would have been only one thing worse than the illegal war against Iraq, and that would have been a legal one.

One reason why anti-war activists are so disgruntled with parliament’s rejection this week of an inquiry into the Iraq war is because they wanted to use the opportunity to expose the war’s illegality – again. Chris Coverdale of Action Against War said it is “time to hold an investigation, and part of that investigation should be about uncovering the illegality of the war”. Numerous columnists, celebrity barristers and former Blairite comedians have spent the best part of the last three years uncovering the illegality of the war. For them, that has become the killer argument about Iraq: it was against the law. It’s a bit like turning up to a bloody street brawl in which people were seriously injured and killed, and saying: “Hmmm. I think a law has been broken here.”

The predominance of the illegality charge shows that today’s anti-war sentiment is motivated less by genuine anti-imperialism than by a kind of dinner-party distaste for the consequences of this particular war. It is the Gray’s Inn brigade, some of them former friends of the PM, effectively saying: “Oh dear, this war doesn’t reach our standards of proof. Let’s call it off.” It is a legalistic version of the Vatican’s “just war” test, and about as radical. Anyone seriously concerned with challenging the Iraq war – and more importantly the post-cold war culture of western interventionism that gave rise to it – should insist that this intervention was immoral, not illegal. War is far too important a matter to be left to lawyers and judges.

The focus on illegality is frustrating for three reasons. First, it is based on the fanciful notion that there was a golden age, pre-President Bush, when international law kept the world in order and allowed peace to reign supreme. Bush is often accused of trampling all over 60 years of UN rules and regulations and giving rise to an era of illegal warfare for oil, land, prestige, whatever. This is an idiots’ guide to international relations. It misses out the cold war period from 1945 to 1989, when western powers launched numerous wars and invasions against supposedly equal sovereign states, including in Aden, Korea, Vietnam, Grenada and Panama. And it misses out the post-cold war period, dominated by Clinton and his cling-ons, when there were “humanitarian wars” in Iraq, Somalia, Haiti, Yugoslavia and Sierra Leone. There has never been a time when the niceties of international law or the existence of the UN stopped western powers from carrying out barbaric acts.

Second, some of the very same people bleating about the illegality of the Iraq war were cheerleaders-in-chief of earlier illegal wars. The Guardian, for example, has been at the forefront of denouncing the Iraq war for being illegal; last year it published extracts from Philippe Sands‘ book Lawless World, which slated Bush and Blair for their cowboyish disregard for international law over Iraq. Yet seven years ago, during the Kosovo crisis, the Guardian was at the forefront of demanding an illegal bombing campaign in Yugoslavia. A leader in the paper criticised those who said Clinton and Blair should wait for proper backing from the UN, questioning the notion that the UN is “the only legitimate law-giver”. The UN constitution is a “recipe for inaction”, it said. “Its imprimatur cannot be the sole trigger for international action to right an obvious wrong.”

Or consider Sands himself. When I ran into him at a public meeting last year, he admitted that he didn’t have a problem with the first Gulf war because it was “legal” – it was justified by UN resolution 678 which provided for the expulsion of Iraqi forces from Kuwait. But what about its consequences? In a seven-week period, around 250,000 bombs were dropped, killing, according to a report in the British Medical Journal, tens of thousands of Iraqis (compared with around 150 Allies who died). Around 80% of Iraq’s water, sewage and electrical facilities were damaged or destroyed. The war was followed by internal strife – including the Shia uprising in the south that was viciously suppressed by Saddam – and by UN sanctions that caused further extreme hardship. The war also gave rise to a decade of interventionism in Iraq: to bombing raids over no-fly zones in the north and south, weapons inspections from 1991 to 1998, Blair and Clinton’s bombing campaign of late 1998, and finally the second Gulf war of 2003.

Yet according to the “legal war” theorists, this first invasion of Iraq was OK, because there was a piece of paper that made it “legal”. This exposes the profound moral bankruptcy of legalistic arguments over war. With the backing of the UN, wars that kill and main tens of thousands of people are apparently fine; without the backing of the UN, they apparently are problematic. And sometimes, just for the hell of it, wars that don’t have the backing of the UN (Kosovo) are also fine. Judgements are made not from the basis of what is good for humanity, or from any analysis of what terrible consequences the war will have for those on the receiving end, but rather from the lawyerly approach of making sure that all the boxes are ticked and all the right procedures were followed. Legal niceties are elevated over people’s lives and livelihoods.

Third, the focus on legality/illegality misses out one important point: if anything, a legal war is worse than an illegal one. In implicitly arguing that wars must be legal, that legal is good and illegal is bad, anti-war activists and commentators are effectively calling for even more coherent and ruthless wars of intervention. For the 2003 invasion of Iraq to have been legal it would have required even more international support, more states lined up against the collapsing Ba’athist regime and the beleaguered Iraqi people, more of a consensus that Iraq was a threat to the world and thus needed to be suppressed. A legal war would have been even more devastating for Iraq than the illegal war has been.

Forget questions of legality. They shouldn’t even come into it. Like the humanitarian attacks on Somalia, Yugoslavia and Afghanistan before it, the invasion of Iraq was immoral and destructive – which means that even if, in legal terms, it had been right, it would still have been wrong.