The signatories of the Budapest Memorandum were Ukraine, Kazakhstan, Belarus, Russia, the UK, and the US.

The stipulations of the agreement are essentially as follows:

1. Respect the signatory's independence and sovereignty in the existing borders (in accordance with the principles of the CSCE Final Act).

2. Refrain from the threat or use of force against the territorial integrity or political independence of the signatories to the memorandum, and undertake that none of their weapons will ever be used against these countries, except in cases of self-defense or otherwise in accordance with the Charter of the United Nations.

3. Refrain from economic coercion designed to subordinate to their own interest the exercise by Ukraine, the Republic of Belarus and Kazakhstan of the rights inherent in its sovereignty and thus to secure advantages of any kind.

4. Seek immediate Security Council action to provide assistance to the signatory if they "should become a victim of an act of aggression or an object of a threat of aggression in which nuclear weapons are used".

5. Not to use nuclear weapons against any non - nuclear-weapon state party to the Treaty on the Non-Proliferation of Nuclear Weapons, except in the case of an attack on themselves, their territories or dependent territories, their armed forces, or their allies, by such a state in association or alliance with a nuclear weapon state.

6. Consult with one another if questions arise regarding those commitments.

1 is obviously trash, and has been since 2014. Russia has tried using legal fig leaves to cover 2, but basically everyone - including Russia - is fully aware that it’s complete bullshit. 3 is also useless - and has been since the document was signed, considering how much influence Russia has exerted on Belarus, Ukraine, and Kazakhstan over the last few decades, but particularly since Putin’s ascent to power. 4 is a non-point because the UNSC is and will continue to be categorically useless simply due to the single-veto structure it has. 5 is what Putin threatens every fucking week. 6 is essentially holding hands around the fire and singing kumbaya, which is manifestly idiotic in this context.

The current situation:

• One signatory (Ukraine) is under attack from another (Russia), and those attacks were, to a significant degree, enabled by a third signatory (Belarus), which itself has been effectively subsumed by another signatory (Russia)
• One signatory (Kazakhstan) can’t feasibly do anything, and is additionally already in a semi-sketchy position with another signatory (Russia)
• the remaining signatories (US; UK) have repeatedly sought UNSC interventions, which have and will continue to fail to pass due to - as noted above - Russia applying their veto as a rule. This is the only enforcement mechanism in the entire thing, and it is effectively a statement of guaranteed bureaucratic inaction.

For real: retrospectively, Ukraine (and Kazakhstan and Belarus) should have held out for WAY stronger enforcements clauses, but (and this part is basically and educated guess) the US and UK were in the “woooo Cold War DONE” mindset, and Russia probably had a rough idea of their current situation in mind, and thus had a vested interest in making the defensive arrangements more or less meaningless.