What is the OPCW, and Can It Referee on Chemical Weapons in Syria?

Inspectors from the Organization for the Prohibition of Chemical Weapons were seeking on Tuesday to enter Douma, a suburb of Damascus, where the United States and Western allies say the Syrian government dropped chemical weapons.

Syria and its main backers, Iran and Russia, say claims of chemical weapons use were concocted by rebels, rescue workers and the West.

Syrian state media said on Tuesday that inspectors had entered Douma. The organization would not comment on those reports.

It is the second time recently that the organization has been thrust into a geopolitical crisis — another high-profile case, the poisoning of a Russian former spy and his daughter in Britain, also drew attention to the group.

The organization is among the few groups to have received a Nobel Peace Prize, which it did in 2013. But what is it and how do its investigators work? And what weight do its conclusions carry?

The organization works with the 192 countries that have signed the Chemical Weapons Convention, an international agreement that “prohibits the use, development, production, stockpiling and transfer of chemical weapons.”

Its job is to monitor compliance with that treaty, and to work toward ridding the world of chemical weapons. It also has a role in verifying the elimination of those weapons.

The group describes itself as “an independent, autonomous, international organization with a working relationship with the United Nations.”

In 2013, Syria signed the convention and agreed to eliminate its chemical weapons stockpiles. On a joint mission with the United Nations, the organization arranged for the transport of all chemical weapons the Syrian government had declared for disposal overseas.

Over 96 percent of state-declared stockpiles around the world have been destroyed under the watch of the organization. However, as seems to be the case in Syria, that doesn’t necessarily mean that countries no longer have chemical weapons, because there is no way to guarantee that they declared everything they had.

The organization was not created to work in battle zones and has had to adapt to send its inspectors to countries at war. In 2014, allegations of chemical weapons use in Syria prompted the group to dispatch a fact-finding mission to the country, the first time it had sent a team to an area of active conflict. (They first visited Syria in 2013.)

Collecting samples while making sure they can be used for evidence takes time, and such missions can turn investigators into targets. While working in Syria in 2014, for example, their convoy came under fire.

Last year, while looking into further allegations of chemical weapons use in Syria, investigators did not visit the town of Khan Sheikhoun because of security fears. Instead, they relied on witness accounts and samples collected from the site. That opened their conclusions to criticism from Russia and Syria, which contended that Damascus had disposed of all its chemical weapons.

No. The organization’s job is to establish whether chemical weapons were used, not who used them.

“It’s dealing with things it wasn’t really intended to deal with,” said Richard Guthrie, a chemical weapons expert and editor of CBW Events, a website that tries to document uses of chemical and biological weapons.

When the Chemical Weapons Convention was being negotiated, Guthrie said, “the concern was large-scale use of chemical weapons on the battlefield — that had happened in the Iran-Iraq war.” But that is different from identifying the relatively small-scale use of chemical weapons, like the alleged case in Syria, or the attack on the spy and his daughter in Britain.

Until the end of last year, the organization had a mandate to pass on its findings to a Joint Investigative Mechanism, established by the U.N. Security Council, which would try to identify the perpetrators of attacks. But last year Russia vetoed the extension of that mandate.

That leaves a disconnect: Even if the organization finds that chemical weapons were used in Douma, the question of who is to blame could remain unresolved.