@decodingtrolls (I preface this by saying that I’m not all caught up on this specific issue, and am merely raising hypothetical questions proponents of this theory have to grapple with.) So I’m not specifically thinking of consequences flowing from a UNGA decision, but from more general sources of law like the UN Charter or other treaties, customary law, and general principles. For example, if one is raising the doubts as to the legal capacity and/or authority of a supposed successor state (which claims to succeed legal authority, rights, and duties from an earlier failed state), then one could say that the if the successor state’s capacity to enter into specific relations were somehow circumscribed then all actions flowing from that are void. That is at least one issue that has to be addressed. The countervailing consideration to that kind of objection would be geopolitical. Obviously, international law and affairs are rarely or never purely legal in nature. As a matter of practicalities, I think many states including legitimate permanent members of the UN SC will be very hesitant to suggest completely voiding all actions that have been taken by the Russian state at the UN SC since the time it was said to have been given a permanent seat. One could point to any of the SC decisions where the Russian state have voted on the same side as the Americans and the Europeans. Would the latter parties really wish to void those decisions taken by the Russians? I doubt so.