Let’s not forget that until a few months ago it was literally illegal to even call this war a war in Russia. But today, it’s not just a war, it’s a defensive ear, if you go by Russian state media (a defensive war that is somehow being fought entirely on another country’s territory).
Russia figured out the magic trick to modern annexation. International law now mostly holds that you can't take land in a war, but that a country's sovereignty arises from the democratic will of the people living there. So Russia just invades under any pretense it likes, and holds "elections" where they get "the will of the people" to be whatever they tell it to be. Like joining Russia.
It's a sham, entirely, but it means they can tell their own people that they are following the law and it's everyone else that's against them.
And so now they can say "look, we did the song and dance that makes this Russian land, so we're defending 'our' people now".
A bit like Iraq and Afghanistan (and Vietnam, Korea, ...)
Technically not true.
They've proclaimed most of these battlefield territories their own, so that is now a technically correct statement.
So, more on how it is sold to the Russian people, rather, than there being anything technically correct about it, right? Because if it's the latter, then I suppose the closes would be "internationally accepted". And, none of the currently occupied regions, including Crimea, is recognized as such.