土耳其紡織品案 GATT第二十四條 關稅同盟 區域貿易協定 GATT 1994釋義瞭解書 自由貿易區 優惠性原產地規則 Turkey-restrictions on imports of textile and clothing products GATT article XXIV Customs union Regional trade agreement Understanding on the interpretation of article XXIV of the general agreement on tariffs and trade 1994 Free trade area Preferential rule of origin