Four years ago President Obama said that the use of chemical weapons in Syria was a red line that would change his “calculus” about U.S. intervention in the region. He later backed away from enforcing that red line with a U.S. military strike on Syria. Instead he worked out an agreement with Russia in which Syria promised to give up all of its chemical weapons.

Today, a UN investigation has concluded Syrian helicopters launched chemical attacks on two occasions, one in 2014 and one in 2015. From Politico:

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.

Reuters reports this now sets up a showdown in the UN security council:

The results set the stage for a Security Council showdown between the five veto-wielding powers, likely pitting Russia and China against the United States, Britain and France over whether sanctions should be imposed in the wake of the inquiry.

“It is essential that the members of the Security Council come together to ensure consequences for those who have used chemical weapons in Syria,” U.S. Ambassador to the United Nations Samantha Power said in a statement. “We strongly urge all states to support strong and swift action by the Security Council.”

Here’s Obama’s original discussion of the red line in Syria:

And here he is after backing away from U.S. military action saying he never set up a red line:

Finally, here’s Jeffrey Goldberg’s account of how Obama decided to abandon the red line at the last moment: