Blast from the past - There WERE chemical weapons in Iraq, from the 1980's, built under US cooperation
Remember why it was so important for "us" to go into Iraq to topple Saddam Hussain's sovereign government? I'm not talking about the real reason - access to Iraq's oil fields - but the reason we were told. Remember warnings of mushroom clouds, and Saddam's chemical and biological weapons research programs? The programs for which zero evidence was found once Western forces entered the country and toppled the government? When then-Secretary of State Colin Powell was sent to the UN Security Council to sell the "world" on the idea of launching a War in Iraq, he told everyone a pack of lies.
But now, according to the NY Times, there were chemical weapons in Iraq. The weapons weren't from an active chemical weapons program however, because no such program existed. These weapons were left over from the 1980's during the Iran-Iraq war when the US Government was helping Iraq build those weapons.
I should mention that since this is the NY Times doing the reporting, we should take it with a grain of salt. First, the NY Times was explicitly used by the political players in Washington as a mouthpiece for the propaganda campaign that successfully sold us on the Iraq War. It's likely the NY Times is being used again. Why is this information being released now (hint: several times the article linked above the weapons were primarily found in territory now controlled by ISIS)? Why not a couple years ago or why not a couple years into the future?
The article describes how US troops on search-and-destroy missions (they were looking for weapons to destroy to ensure the materials wouldn't end up in IED's) were sometimes finding old buried caches of chemical weapons. Mustard gas, Sarin, etc. The soldiers were never told ahead of time they might find such old weapons, and whenever the weapons were found the story was hushed up. In some cases the solders became "contaminated" with the agents.
Most of the chemicals had been found near the Muthanna State Establishment, described as "the center of Iraqi chemical agent production in the 1980s". ISIS has held that compound since June 2014.
Supposedly the old weapons don't pose a threat - the agents having become mostly ineffective. But, according to the article, insurgents were inventive about using those agents as decayed as they were to cause damage.
The secrecy imposed by the US forces to hide knowledge that these old weapons had been found violate the Convention on Chemical Weapons. Under that convention chemical weapons are supposed to be "secured, reported and destroyed in an exacting and time-consuming fashion". Instead, while the US forces did destroy some of the chemical weapons they'd found, they didn't get to all of them, some were lost, or left unsecured (presumably now stolen), etc.