That explanation sounds fishy to me. If something doesn't work then there's no need to ban it.

> If something doesn't work then there's no need to ban it

Did you read the article?

Chemical weapons provide no benefit to a modern army. They do, however, to simpler armies. So the world's militaries, who command modern armies, came together and banned them.

Put another way, the U.S. military gains nothing from chemical weapons over high explosives. The Taliban, on the other hand, might.

In addition to what the other commenter said, it's virtue signaling.