"People’s Republics of Donetsk and Lugansk." break away republics recognized as independent by Russia. Right to self determination? We all know what happened when a few of the states tried to break away from The USA so What's next?
There are some quite complicated legal requirements for a group of people to be able to legally claim a right to self-determination under international law. We would need to examine whether there was anything particularly distinctive about the peoples of Donetsk and Legansk that would make them fundamentally different from Ukrainians or Russians, for instance. Also, if only one nation (Russia) is recognising this supposed "right", the right may be difficult to establish legally.