To clarify, the upholding of the security assurance is still left up to the discretion of nations in the agreement, based on how important non-proliferation of nuclear weapons is to them. It seems that recently, nuclear proliferation is no longer a concern for the US, hence they no longer enforce this agreement, which is their right, for better or worse.
I'm not sure any of these things are really enforceable short of someone taking military action? I think Russia has broken loads of agreements re Ukraine and nothing very much usually happens.
Even NATO article 5, I'd expect if Russia rolls into Lithuania Trump would ignore it.
The two main enforcement mechanisms are economic sanctions and military aid, which even the EU has been involved with. Economic sanctions haven't had much impact but coupled with military aid has stopped Russian progress in the invasion. The problem is, with the US pulling out, EU big shoes to fill with military aid.
The agreement has no explicit terms for whether or not nations must enforce it, that's left up to the nations to decide on their own. It was intentionally written this way, otherwise Russia would have never agreed to it.
You keep misunderstanding. As I have already stated, the agreement lacks formal enforcement mechanisms, how it is upheld is up to the agreeing nations to figure out. In 2014 that was economic sanctions. In 2022 that was military aid. This is how political agreements work.
