The ozone treaty refers to the Montreal Protocol on Substances that Deplete the Ozone Layer, which is an international agreement aimed at protecting the stratospheric ozone layer by phasing out the production and consumption of ozone-depleting substances such as chlorofluorocarbons (CFCs), halons, and other chemicals that contribute to ozone depletion. The treaty was adopted in 1987 and has since been ratified by more than 200 countries around the world.