Asklemmy

To take this in a different direction, legal or not (considering the "higher power" generally gets to define what is and isn't legal and might do so for its own benefit rather than in the best interest of everyone, if there even is such a thing), how can it be determined if a subset of a power structure breaking away from that power structure is a good thing or bad thing? What arguments other than "we'll use force" are there to support a region needing to remain under the thumb of a power they no longer wish to serve?

See: American civil war

Didn't have a way to legally secede from Britain

No but there's no law against expelling a state from the union. Kind of a reverse secession if you can piss trump off enough for him to actually do it (no law saying that only Congress can expel them, so it would go to the courts).

Define "legal".

No. A full breakdown here https://youtu.be/1dhvry6E0jA

We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness.--That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed, --That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness.

The Constitution of the US of frickin A