集団安全保障条約第4条

Article 4
If one of the Member States undergoes aggression (armed attack menacing to safety, stability,
territorial integrity and sovereignty), it will be considered by the Member States as aggression (armed attack menacing to safety,
stability, territorial integrity and sovereignty) to all the Member States of this Treaty.

In case of aggression commission (armed attack menacing to safety, stability, territorial integrity and sovereignty)
to any of the Member States, all the other Member States at request of this Member State
shall immediately provide the latter with the necessary help, including military one,
as well as provide support by the means at their disposal in accordance with the right to collective defence
pursuant to article 51 of the UN Charter.

The Member States shall immediately inform the United Nations Security Council on the measures
taken on the basis of this article. When implementing these measures, the Member States
shall adhere to the relevant provisions of the UN Charter.

これ自衛権の話してるから宣戦布告とか関係ないと思うで
ルガンスクとドネツクはまだ加盟国じゃないし
承認してない国もあるんやろ？