Following a vote earlier today the Organisation for the Prohibition of Chemical Weapons (OPCW) is now authorised not only to investigate chemical attacks but also -- crucially -- to identify whoever was responsible.

The decision came from a special session of states parties to the Chemical Weapons Convention which overwhelmingly approved a British proposal to change the rules. It needed a two-thirds majority to pass but despite opposition from Syria and obstructive tactics from Russia and Iran, 82 countries voted in favour and only 24 against.

A key part of the newly-approved document (full text here) says: "Whenever a chemical weapons use occurs on the territory of a State Party, those who were the perpetrators, organisers, sponsors or otherwise involved should be identified ..."

Referring to several specific cases, the document condemns the use of a Novichok nerve agent in Britain last March, the use of a VX nerve agent against a North Korean citizen last year and the use of chemical weapons by the so-called Islamic State in Iraq and Syria.

Those attacks -- and many more during the conflict in Syria -- have been threatening to normalise the use of chemical weapons, seriously weakening the Chemical Weapons Convention which until recently was a very successful example of international cooperation.

Over the last few years the OPCW has produced numerous reports on the chemical attacks in Syria but while its investigators have uncovered a wealth of information about what happened, the rules did not allow them to identify the culprits.

To address that problem, the UN Security Council set up a "Joint Investigative Mechanism" (JIM) with power to apportion blame. Last year it issued a report blaming Syrian government forces for the sarin attack in Khan Sheikhoun and shortly after that Syria's ally, Russia, put a stop to the JIM's activities by vetoing a renewal of its mandate.

The effect of today's decision is that efforts by the OPCW to identify perpetrators of chemical attacks can no longer be blocked by a veto in the Security Council. It also means the OPCW will be able to compile evidence that could be used in eventual prosecutions and, hopefully, that prospect may help to deter future attacks. In addition, if there's more prospect of bringing perpetrators to justice there may be less temptation to respond to chemical attacks through bombing.

This change in the rules comes as the OPCW's report on the alleged chemical attack in Douma, Syria, last April is imminently expected. There were reports that it was due to be published early this week, but it appears to have been delayed. This may be an indication that it is being revised in the light of the OPCW's expanded mandate.