When it comes to the third basic requirement, which is that, in general, barriers should not increase for third parties, things become more complicated. Given that free trade agreements are much more widespread than customs union unions, it seems that this is not the case. With regard to free trade agreements, there is no need to negotiate a common external tariff and the tariff applicable to non-parties should not change in general. But there are other channels through which discrimination against outsiders under free trade agreements can increase. The first potential problem arises when developing countries apply tariffs below the maximum levels they should not exceed under WTO rules. This gives them the flexibility to erect barriers to third parties, while respecting or maintaining preferential tariffs for free trade partners. Mexico`s trade response to the 1994 peso crisis is a striking example, when it did so in the context of the implementation of NAFTA. 18 Other studies have shown that free trade agreement partners are more likely to use remedial measures against allegedly unfair trade (anti-dumping and countervailing duties) against outsiders than against each other. 19 In addition, the increase in the RTA has come to an end to the overlapping phenomenon of membership. This can hinder trade flows when traders struggle to meet multiple sets of trade rules. As the scope of the ATR extends to areas of action that are not regulated multilaterally, the risk of inconsistencies between the various agreements may be increased.
Most of the previous ATRs involved tariff liberalization and related rules, such as trade defence, standards and rules of origin. Increasingly, ATRs have adopted the liberalization of services as well as obligations on service rules, investment, competition, intellectual property rights, e-commerce, environment and work. This could result in regulatory confusion and implementation problems. 56 “Working Group IV Report on Organizational Issues,” doc. L/327, 22 February 1955, paragraph 39: “The Group has addressed the issue of the extension by the Contracting Parties of the benefits of the agreement to non-contracting parties through bilateral agreements. During the discussion, it was pointed out that non-contracting parties often enjoyed all the benefits of the agreement without having to meet its obligations and that this situation could discourage other countries rather than encourage them to join. However, most members of the group felt that the position that a contracting party wished to take in this regard vis-à-vis a non-contracting party was within the purview of each contracting party. Many WTO members continue regional economic integration with both other members and non-WTO members. The resulting departure from the principle of the most favoured nation must be justified in accordance with the relevant WTO provisions.