BTW: Can a NATO country shoot a target at territory of Ukraine over the border, like Russia and Belarus do?
And it won't happen. Although... the last few days have shown extraordinary events that I never expected. The EU approving 500 Million for weapon purchases for Ukraine, countries supplying fighters after two days delay, officiaks saying that their are fine with their citizens volunteering to fight for another state army (illegal pretty much everywhere), plans to supply troop movement intelligence... That's all just a very small step from active participation.
This is the most significant shift in European politics since the fall of the Soviet union.
We'll see what happens if Russia continues to indiscriminately massacre civilians by using MLRS into dense urban centers.
But Russia is ignoring those laws. What Russia is doing is called "war of aggression": https://en.wikipedia.org/wiki/War_of_aggression
"A war of aggression, sometimes also war of conquest, is a military conflict waged without the justification of self-defense, usually for territorial gain and subjugation."
Right now, it seems NATO strategy is severe financial sanctions while providing arms to Ukrainian forces.
I do realise the risk of nukes at that point but in the hypothetical situation that nukes remain MAD
Also it is quite clear Putin won't lose his face no matter what, and has reached the point of better dead than sorry.
Very sadly how many has he already taken down with such attitude.
Having Cold War situations again isn't desirable of course but it's kind of battle tested to not lead to further, direct, escalations.
For the record, Russia also said sanctions would be considered an act of war. ¯\_(ツ)_/¯
That aside Russia coming up with it's own reasons for engaging in war with a country is different than Russia having internationally recognized reasons for engaging in war with a country.
Can you explain? Is there another internationality, except UN, which has authority to allow wars?
Kind of. International law is made up of both treaties and customary international law, which is (to oversimplify) basically a distillation of state practice. Think of it as almost analogous to statues vs. common law.
For example, while the U.S. is not a party to the U.N. Convention on the Law of the Sea, it recognizes most of its tenets as customary international law. (This is also why it regularly conducts freedom of navigation passages in the South China Sea, to prevent China's ownership claim from becoming customary international law.)
If a large number of nations (say, NATO?) agreed that another lawful basis for the use of force (LBUF) existed, beyond the right of self-defense or an UNSCR, that could become customary international law. The hot topic in this area right now is humanitarian intervention, which NATO cited in its Kosovo intervention and which the UK recognizes as a CIL LBUF. This gets meta real fast, since even though a large number of nations reached consensus on using it as justification for Kosovo, they haven't reached a consensus that there is a consensus on using it. Only the UK explicitly recognizes it as CIL, last I checked.
So what you see instead is this kind of academic song and dance where, e.g., the U.S. de facto is using humanitarian intervention to justify intervention in Syria but de jure relies on a mildly stretched interpretation of self-defense instead.