It is in relation to the GATT agreement in 1947 where restrictions on trade were removed.
What does "Cláusula de la nación más favorecida" mean?
In international economic relations and international politics, most favoured nation (MFN) is a status or level treatment accorded by one state to another in international trade. The term means the country which is the recipient of this treatment must, nominally, receive equal trade advantages as the "most favored nation" by the country granting such treatment. (Trade advantages include low tariffs or high import quotas.) In effect, a country that has been accorded MFN status may not be treated less advantageously than any other country with MFN status by the promising country.