The UK has just set out its new trade strategy, and one point in there is that it will be joining the MPIA:
The WTO has an almost unique function to resolve trade disputes. That trade dispute system is busier than ever but, since 2019, it has lacked an appellate function, limiting the ability to resolve the disputes brought before it. The UK has been active in the work to resolve the impasse and continues to support it. However, there is no immediate prospect of the impasse being resolved. In the interim, a number of members have established the Multi-Party Interim Appeal Arbitration Arrangement (MPIA), a temporary arbitration arrangement for resolving appeals while the dispute settlement system remains only partially operational.
The UK will now join the Multi-Party Interim Appeal Arbitration Arrangement, reinforcing our commitment to an effective rules-based international trading system and to defend UK trading interests.
The UK remains dedicated to re-establishing a fully functioning WTO dispute settlement system and will continue collaborating with other WTO Members to achieve this objective. Joining MPIA sends a clear signal that the UK is committed to the principles of free and
fair trade and that we will champion progress wherever and whenever necessary.
With the UK on board, it's worth thinking about the prospects for additional WTO Members joining. Here are the WTO Members that have been involved in WTO disputes as the complainant or respondent since January 1, 2018 but are not currently parties to the MPIA: Argentina, Armenia, Dominican Republic, Egypt, India, Indonesia, Kyrgyz Republic, Morocco, Panama, Qatar, Russia, Saudi Arabia, South Africa, South Korea, Taiwan, Thailand, Tunisia, Türkiye, UAE, United States, Venezuela, and Viet Nam.
With regard to the U.S., although I recently wrote a piece on what it would take for the U.S. to join a version of the MPIA, I don't anticipate that happening any time soon.
As for other Members, the decision may depend on internal and external political considerations, as well as more practical concerns about whether the Member is the respondent in current WTO disputes and may want to preserve the ability to appeal into the void, or is a complainant that would like to avoid appeals into the void. With that in mind, perhaps the following are possible leading candidates for joining: Argentina, Indonesia, Panama, South Africa, and South Korea. However, to be certain about any of this, it would take more knowledge about the situation of each of these countries than I have.
