As the Montreal Protocol regime has evolved and grown more complex since 1987, developments have occurred which have not, by and large, been foreseen - though, arguably, some of them should have been. This chapter examines two areas of particular concern in respect of the international trade in ozone-depleting substances (ODS). Non-compliance with the reporting provisions of the Montreal Protocol has been a problem for several years; data have frequently been submitted late or in an incomplete form, or not submitted at all. The Implementation Committee of the Montreal Protocol is responsible for dealing with cases of non-compliance and reporting back to the Meeting of the Parties with recommendations. Evidence of smuggling in the European Union is more difficult to come by. The problem seems to be genuinely smaller than in the US because of the relative lack of mobile air-conditioning systems (MACS) in European cars, and also because of the general absence of CFC taxes.