At the international level, there are two important open access databases developed by international organizations for policy makers and businesses: these occur when one country imposes trade restrictions and no other country responds. A country can also unilaterally relax trade restrictions, but this rarely happens. This would penalize the country with a competitive disadvantage. The United States and other developed countries do so only as a kind of foreign aid to help emerging countries strengthen strategic industries that are too small to be a threat. It helps the emerging market economy grow and creates new markets for U.S. exporters. Let us assume, for example, that Japan sells bicycles for $50, that Mexico sells them for $60, and that they both face a US dollar of $20. If tariffs on Mexican products are removed, U.S. consumers will transfer their purchases of Japanese bicycles to Mexican bicycles. The result is that Americans will buy from a more expensive source, and the U.S.
government does not receive customs revenue. Consumers save $10 per bike, but the government loses $20. Economists have shown that when a country enters such a “trade” customs union, the cost of trade diversion can outweigh the benefits of enhanced trade with other members of the customs union. The result is that the customs union could degrade the country. As a multilateral trade agreement, GATT calls on its signatories to extend the status of the Most Preferred Nation (MFN) to other trading partners participating in the WTO. MFN status means that each WTO member enjoys the same tariff treatment of its products in foreign markets as the “preferred” country that competes in the same market, thus excluding preferences or discrimination from a Member State. Unlike a customs union, parties to a free trade agreement do not hold common external tariffs, i.e. different tariffs, or other policies concerning non-members. This function allows non-parties to free themselves as part of a free trade agreement by entering the market with the lowest external tariffs.
Such a risk requires the introduction of rules for determining which products originate may be preferred under a free trade agreement, which is not necessary for the establishment of a customs union.  In principle, there is a minimum processing time leading to a “substantial processing” of the products, so they can be considered original products. By the definition of products originating in the PTA, the preferential rules of origin distinguish between domestic and non-origin products: only the former are eligible for preferential tariffs provided by the ESTV, which must pay the import duties of the MFN.  The European Union is now a remarkable example of free trade.