Bashar Assad's regime was responsible for at least two cases of using chlorine in his country's civil war. | Getty U.N. report: Assad again used chemical weapons, defying Obama

Even after he supposedly turned over his entire stockpile of chemical weapons three years ago, Bashar Assad is still crossing Barack Obama's "red line," a U.N. investigation has found.

U.S. officials confirmed Wednesday that the probe had determined that the Syrian president and his regime were responsible for at least two cases of the deadly use of chlorine in the Arab country's civil war since 2013. Investigators also blamed the Islamic State terrorist group in an incident involving mustard gas.


The findings give ammunition to Republicans critical of the U.S. president's handling of the crisis in Syria, especially his decision not to militarily intervene in 2013 even after it became clear Assad was not heeding his warning that using chemical weapons would cross a "red line." The investigators' findings also could set up a showdown between the U.S. and Russia, which has long backed Assad, as the U.N. Security Council decides what to do in response.

Samantha Power, the U.S. ambassador to the United Nations, issued a stern statement on the report, condemning the "horrific and continuous use of chemical weapons by Syria."

"It is essential that the members of the Security Council come together to ensure consequences for those who have used chemical weapons in Syria," she said. "It is essential that all state and non-state actors immediately cease any chemical weapons use. We strongly urge all States to support strong and swift action by the Security Council."

The White House, however, issued a more measured response, that, while condemning the chemical weapons use in the "strongest terms," did not emphasize the need for an urgent reaction from the international community.

"The United States will work with our international partners to seek accountability through appropriate diplomatic mechanisms, including through the United Nations Security Council and the [Organization for the Prohibition of Chemical Weapons]. We urge all U.N. member states and parties to the Chemical Weapons Convention, including Russia and Iran, to participate in this effort," said Ned Price, spokesman for the White House-based National Security Council.

Syria devolved into civil war in 2011, and in 2012, Obama issued his "red line" warning to Assad, which many in the international community believed meant the U.S. would act if the Arab dictator used chemical weapons. The following year, it became clear that the regime was employing such deadly agents, killing hundreds of civilians.

But Obama chose not to stage military strikes against the Assad regime; instead, the Obama administration, along with Russia and other parties, struck a deal with Assad in late 2013 that allowed him dismantle and turn over to international bodies his chemical weapons stockpile. Assad also joined the Chemical Weapons Convention.

It was in many ways a historic, ground-breaking agreement, leading to the disposal of some 1,200 tons of deadly chemical agents through a process guided by the U.N.'s Organization for the Prohibition of Chemical Weapons, or OPCW. Obama has said he is proud of his decision to make a deal, arguing it saved more lives in the long run than military strikes.



But many Republicans have been critical of Obama's unwillingness to stage a military strike on Assad, saying it made the U.S. look weak and emboldened rivals such as Russia. Rep. Ed Royce, chairman of the House Foreign Affairs Committee, told POLITICO in a statement after Wednesday's report that Assad has "made a mockery" of Obama's "red line."

"The White House says it is now 'impossible to deny' the regime repeatedly launched gas attacks against the Syrian people in 2014 and 2015," the California Republican said. "Just a few weeks ago, the Assad regime dropped more barrel bombs on a neighborhood in eastern Aleppo. So what's the president going to do about it?"

Chlorine was not included as part of the agreement with Assad because the product has many legal uses. However, using chlorine as a weapon is forbidden by the Chemical Weapons Convention, which Assad joined as part of the deal. In any case, since 2013, there have been dozens of alleged cases of chemical weapons use in Syria, and this week Foreign Policy reported that the U.N. was worried Assad had not turned over everything he was supposed to under the original deal.

The report delivered Wednesday was from the Joint Investigative Mechanism (JIM), a panel tied to the OPCW. The JIM's investigators looked into nine cases of alleged chemical weapons use in Syria since 2013. The JIM's mandate was to name the perpetrators of the attacks in as many of the cases as it could. But it's up to the Security Council to now determine how or whether to punish those perpetrators.

The Islamic State, which has territory in parts of Syria and Iraq, is already under siege by a U.S.-led coalition. Assad, meanwhile, is fighting U.S.-backed moderate rebels and an array of other groups trying to topple him. His government has been receiving military support from Russia and Iran.

Russia, like the U.S., holds a veto on the Security Council, and it could try to derail any serious attempt to punish Assad. However, it might be willing to agree to some sanctions on the regime. The Russian Embassy in Washington did not immediately respond to a request for comment.

