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 trade agreement database provided by the ITC market access map. Given that hundreds of free trade agreements are currently in force and are being negotiated (approximately 800 according to the rules of the intermediary of origin, including non-reciprocal trade agreements), it is important for businesses and policy makers to keep their status in mind. There are a number of free trade agreement custodians available at national, regional or international level. Among the most important are the database on Latin American free trade agreements, established by the Latin American Integration Association (ALADI) , the database managed by the Asian Regional Integration Center (ARIC) with information agreements concluded by Asian countries and the portal on free trade negotiations and agreements of the European Union.  For example, a nation could allow free trade with another nation, with exceptions that prohibit the importation of certain drugs that are not authorized by its regulators, or unvaccinated animals or processed foods that do not meet their standards.
In general, trade diversion means that a free trade agreement would divert trade from more efficient suppliers outside the zone to less efficient suppliers within the territories. Whereas the creation of trade implies the creation of a free trade area that might not otherwise have existed.