This chapter examines the requirements of Article XXIV of the General Agreement on Tariffs and Trade (GATT) for the formation of free trade areas (FTAs) and customs unions (CUs). First, I examine the requirements for the formation of RTAs under Article XXIV and the various debates surrounding the interpretation of this GATT Article. I then examine the GATT/WTO framework as a trade constitution before proceeding to examine the problems encountered in the examination process of RTAs at the WTO, particularly in relation to defining ‘substantially all the trade’ under Article XXIV (8), ‘interim agreements’ under Article XXIV 5(c); ‘other regulations of commerce’ as well as ‘other restrictive regulations of commerce’ under those Articles. The chapter then examines liberalization of restrictive rules of origin before proceeding to examine the enabling clause as it relates to the formation of RTAs. The chapter then discusses the EC-GSP case and, briefly, the EU-ACP EPA agreements to conclude the chapter. The EPAs are further discussed in Chapter XI.