In 2013, Barack Obama made a bargain with Syria’s president, Bashar al-Assad, brokered by Russia, the latter’s ally. The United States withdrew its threat to attack Mr Assad’s regime for using sarin against Syrians in Damascus that summer. Hundreds died in the deadliest use of chemical weapons since the Iran–Iraq war. Mr Assad denied he had used such weapons, but in return for US restraint his regime agreed to dismantle its chemical weapons programme. Much of the country’s banned substances were thought to have been destroyed, and Syria joined the treaty against their use.

Yet as the years have unfolded, Mr Assad, a ruthless dictator who the world would be better without, has made a mockery of the agreement. Syria’s civil war, now in its seventh year, has been wreathed in toxic fumes. Experts from the UN and the chemical weapons watchdog said the Syrian regime has used helicopters to dump chlorine gas on opponents. Chlorine is not a banned substance, since it has commercial uses, but its use as a weapon is. The watchdog last year said Mr Assad’s forces also used sarin gas, a nerve agent, to kill more than 90 people in Khan Sheikhun. There have been an estimated score or more of incidents of chemical weapons use since then.

These are heinous crimes using weapons of mass destructive terror. It’s not that these weapons kill on any wider a scale than heavy artillery does, but that they kill in a very cruel way. People die in their beds, clutching babies and loved ones. The ability to burn people inside out sends fearful shivers through populations. The use of chemical weapons amounts to official terrorism, corrupting further a corrupt regime. Mr Assad does not care; it has been effective, even in smaller doses than the 2013 attack, to evict insurgents from their sanctuaries, forcing them to keep moving and making it harder to regroup, with consequent demoralisation.

Mr Assad has been allowed to act with murderous impunity because of his backers in Moscow. Russia has vetoed critical resolutions at the UN security council in relation to Syria. To deter Mr Assad from using chemical weapons, the United States, France and the UK are considering military action – although Donald Trump followed bombastic threats by tweeting he never said “when an attack on Syria would take place”. Too large an attack might lead to a dangerous escalation with Russia in a country that Moscow has used as a testing ground for sophisticated weaponry, a fact demonstrated when anti-aircraft fire brought down an Israeli F-16 fighter jet in February.

Vladimir Putin’s Russia has largely fallen out of love with arms control, seeing the rules-based order as a way of reducing its influence and stature in the world. Moscow wants Russia’s power to reflect its gigantic geography rather than its puny economy and almost non-existent political magnetism. Russia is similar to North Korea and Iran in seeking strength through having adversaries. But in eliciting global condemnation they achieve weakness.

In the longer term, the only way to bring back rogue nations into compliance will be through reestablishing the fundamental premise of why arms control agreements exist. Countries enter into them not for the sake of moral principle but because they help to set up the rules for military strategy. Key to this is developing ways to avoid war, minimising the competition between military powers, and curtailing the scope of violence if the fighting does break out. In Syria, the Russians and Iranians have lost sight of these things. Precipitate military action without parliamentary scrutiny will not help. What will is establishing a wider cost for such awful behaviour.

• This article was updated on 12 April 2018 to clarify the Guardian’s stance.

