Each state is unique and, sometimes, there have to be exceptions. For example, Article I said that any trade agreements that existed prior to GATT, such as the British Commonwealth trade preferences, could be retained. The Multifibre Agreement allowed some developed countries, Canada included, to restrict textile imports from developing nations. Article XXIV of the GATT permitted Contracting Parties to enter into separate free trade agreements, such as Canada, the United States and Mexico did under the North American Free Trade Agreement of 1994. In the short term, the effect of a tariff is that it reduces the amount of goods imported thereby improving the international trading position of the country imposing it.
Tariffs also protect domestic producers from foreign competition.
In the long run, tariffs usually lead to an overall decrease in exports as well as imports. However, tariffs are an important source of government income, particularly in the developing world. A non-tariff barrier is an impediment to trade that does not involve a tax on imported goods. Some countries are very creative in finding ways of blocking imports. Japan, for example, has a system of exclusive supplier contracts which make it impossible for a non-Japanese company to distribute its products.