As it became clear in the 1980s that human-derived chemicals were threatening life on Earth, all countries of the world agreed to an international protocol to halt their production.  So, problem solved, right?  Unfortunately, not quite yet...  We recently detected an uptick in CFC-11 emissions indicating that someone, somewhere had been ignoring international law.  Will the Montreal Protocol and the ozone layer survive?  I'm convinced they will, but in large part because the Protocol has included regular assessments from the scientific community on the progress being made.  In this talk I'll discuss the chemical and physical evidence trail we followed that enabled this surprising conclusion, and describe how scientists, the international policy community, and even atmospheric CFC-11 concentrations have responded.