And then, of course, there's the former Soviet Union...

Most African decolonisation was also peaceful.

India's decolonization was also mostly peaceful. What was not peaceful in India was the post-independence separation between Pakistan and India.

pretty much all of these cases were "crumbling/dissolution of empire" or similar. I.e. an opportunity presented by dramatic shift in force balance when dominating force is weakened and thus couldn't stop the process. It wasn't a result of a process legitimate according to the laws at that moment in that geography. And that is exactly my point (it wasn't about peacefulness - if you have obviously prevailing force, the things have good chances to happen peacefully, like in case of Crimea :). It is always about force. Laws, like always, follow the force and legitimaze the separation after the fact.