On Social Media, Medvedev wrote the following:

Western countries that allegedly "approved the use" of their extended-range weapons on Russian territory (regardless of whether we are talking about old or new parts of our country) must clearly understand the following:

1. All their military equipment and specialists fighting against us will be destroyed both on the territory of the former Ukraine and in other countries if attacks are launched from there against the territory of Russia.
2. Russia proceeds from the assumption that all long-range strike systems used by the former Ukraine are already directly operated by NATO military personnel. This is not "military assistance" but participation in the war against us. Such actions can very well become a casus belli.
3. NATO will have to decide how to classify the consequences of possible retaliatory strikes on the equipment/objects/military personnel of individual member countries in the context of Articles 4 and 5 of the Washington Treaty.

In all likelihood, the NATO leadership wants to pretend that we are talking about sovereign decisions of individual countries of the North Atlantic Alliance to support the Kyiv regime, and there is no reason to apply the rule of the 1949 Treaty on collective self-defense here.