In a post last month after Japan joined the MPIA, I said:
Why is Japan making this announcement right now? Hard to say for sure, and there could be a number of things going on, but as Dmitry Grozoubinski pointed out to me, the ongoing panel hearing Japan's complaint in China - AD Measures on Stainless Steel (DS601) has said that it "expects to issue its final report to the parties by the first quarter of 2023." It's definitely worth keeping an eye on developments in that case. No doubt Japan would like to avoid China appealing into the void if it loses, and joining the MPIA now could be a way to prevent that.
Following up on that, earlier this week Japan and China notified the DSB that they have agreed to Procedures for Arbitration under Article 25 in the DS601 dispute to handle any appeal. The panel in DS601 recently updated its schedule to say that it "now expects to issue its final report to the parties in May 2023." It seems like we are headed towards a panel report being issued soon and an MPIA appeal coming after that, although a settlement is always a possibility.
