It was reported in 1993 that BP Chemical, a US company, had a process that it was ready to license to the Iranians, who said they wanted it to produce acrylics. But the plant would also have produced hydrogen cyanide as a by-product, and that was a poison gas. The White House had stopped the deal.
Strict export controls are necessary to block deliberate export of equipment and chemicals needed to manufacture gases for chemical warfare.
Many of the substances sold to countries with chemical weapons programmes are of "dual use", meaning they can have legitimate applications in pesticides, dyes or even ink for ballpoint pens. Developing countries have sometimes portrayed the calls for export controls as "colonialism" by Western countries and advocate instead a worldwide ban on chemical weapons.