BBC:
Who is right?
When withdrawing from the deal, President Trump expressly decided to end „the participation of the United States“ in the arrangement. This unhappy phrasing, repeated by Secretary of State Pompeo, makes it difficult to argue that the US remains a participant only for the purposes of the snapback.
John Bolton himself, National Security Advisor at the time of the withdrawal, asserts that this view is „legally incorrect“, as do all the other participant states and the EU.
The finding of the Security Council president, undoubtedly based on legal advice, also points in that direction. Moreover, the admittedly ingenious US attempt to isolate the definition of „participant state“ from the question of which states are actually participating in the deal does not work.