The Budapest Memorandum which Belarus and Ukraine signed onto giving up nuclear weapons etc was never a treaty. No country wanted to have any legal obligations (or in Greg's words "contractual") to have to go war for either Ukraine or Belarus, so we signed a memorandum with them instead. This provides assurances not guarantees. It's so weakly written, it basically says hey Belarus and Ukraine if you have problems (like being attacked) then you can bring them up to the security council and we will discuss it. The whole thing had already been broken by 2013 because it was supposed to protect Belarus and Ukraine from attacks whether through economic or military means. The US applied sanctions on Belarus in 2013, which led to Belarus to argue that the US was violating the memo but the US argued the Budapest Memorandum isn't a treaty so they didn't have to follow it, and it was basically a big piece of toilet paper. So please never use the word treaty or contracts or guarantees when talking about the Budapest Memorandum.
