And nothing in the Budapest Memorandum requires or even permits a signatory to defend Ukraine against another signatory or anyone else. Obviously the Ukrainian government would ask for help in such a case, but there is no current treaty obligation to provide it.
Complicating this is that Russia claims Yanukovich is still the legitimate leader of Ukraine and that their actions thus far have his blessing, meaning their troops are not attacking Ukraine but supporting it against an armed insurrection. Nobody outside Russia's circle of friends believes that, of course, but its the fig leaf they are using.
Sir Anthony Brenton (UK Ambassador to Russia 04-08): "If indeed this is a Russian invasion of Crimea and if we do conclude the [Budapest] Memorandum is legally binding then it’s very difficult to avoid the conclusion that we’re going to go to war with Russia."
Key emphasis on and if we do conclude the [Budapest] Memorandum is legally binding. That's a rather big if. But realistically, no one is going to care, because the west still isn't going to war with Russia over this.
Edit: Technically, if it wasn't approved by the US Senate, then its legally just scrap paper.
All sides have been saying a lot of shit that is not exactly true over the past week. Here is the full text of the memorandum: http://www.larouchepub.com/eiw/public/2014/2014_1-9/2014-08/.... Nothing in there provides an obligation to defend Ukraine from a third party.
Complicating this is that Russia claims Yanukovich is still the legitimate leader of Ukraine and that their actions thus far have his blessing, meaning their troops are not attacking Ukraine but supporting it against an armed insurrection. Nobody outside Russia's circle of friends believes that, of course, but its the fig leaf they are using.