- Montreal Protocol on Substances that Deplete the Ozone Layer : A Montreal Protocol on Substances that Deplete the Ozone Layer is the Montreal Protocol and its amendments control the phaseout of ozone depleting substances production and use. Under the Protocol, several international organizations report on the science of ozone depletion, implement projects to help move away from ozone depleting substances, and provide a forum for policy discussions. In the United States, the Protocol is implemented under the Clean Air Act Amendments of 1990. See ozone depleting substance, ozone layer.