A multilateral treaty is a particular form of multilateral treaties. A multilateral treaty is a contract between a limited number of states that have a particular interest in the subject of the treaty.  The main difference between a multilateral treaty and other multilateral treaties is that the availability of reserves is more limited by a multilateral treaty. Given the limited nature of a multilateral treaty, full cooperation between the parties is necessary for the purpose of the treaty to be respected. Therefore, reservations about multi-lateral contracts are not admissible without the agreement of all other contracting parties. This principle is codified in international law by Article 20, paragraph 2 of the Vienna Convention on Treaty Law: a final argument is that plurilaterals multiply and create confusion in the trading system due to conflicting rules, including rules of origin, which greatly increase uncertainty in the system and pose business compliance problems. A more subtle argument, and I want to say to my trade colleague, Scott Miller, that he has explained this argument, is that multilateral agreements discourage countries from making multilateral concessions. If, for example, you are in Vietnam and, as a result of the comprehensive and progressive trans-Pacific Partnership (CPTPP) agreement, you now have zero tariffs with Japan (and other partners) on a wide range of issues, you are much less interested in a multilateral agreement that would reduce tariffs for all , because it would sweeten the advantage you have with Japan. There are advantages to being in the tent, so to speak, but the more you let the tent in, the smaller your particular advantage will be. The curve has slowed in recent years, but the trend is evident and coincides with the difficulties of the Doha Round.
In 2001, 91 cumulative regional trade agreements were in force and 305 are in force. This certainly indicates that the failure of one has influenced the success of others, but that does not mean that we have to choose. It is useful to continue efforts towards multilateral agreements, but knowing that failure will likely lead to more regional agreements. This is not to say that Europeans are not Pharisees, but it does indicate that it could be a smart policy to follow both paths at the same time.