Here it is again:
"The memoranda, signed in Patria Hall at the
Budapest Convention Center with US Ambassador
Donald M. Blinken amongst others in attendance,
[2] prohibited the Russian Federation, the United Kingdom and the United States from threatening or using military force or economic coercion against Ukraine, Belarus, and Kazakhstan, "except in self-defence or otherwise in accordance with the
Charter of the United Nations." As a result of other agreements and the memorandum, between 1993 and 1996, Belarus, Kazakhstan and Ukraine gave up their nuclear weapons."
You're right that when Russia took Crimea back the group did nothing. Same when Russia took the Donbas, until Trump gotcvin and gave them Javelins and other military aid.