The Constitution is silent on it.
Use reason here. If states don’t have the option to leave, their people are not free.
Why would it be acceptable for an Estonia, Ukraine, Caledonia, Scotland, or Quebec to leave their unions, but not, say, a Delaware?
>>Why would it be acceptable for an Estonia, Ukraine, Caledonia, Scotland, or Quebec to leave their unions, but not, say, a Delaware?<<
They are not part of the USA and governed by the USC AND they continue to operate as countries, just countries that have pledged fealty to an Emperor.
When a territory joins the US it says “this is now a State.” No more, no less than any other and the history becomes legally irrelevant. A country that joins the EU continues to be a country, it just promises to adhere to a bunch of rules and regulations shared by other countries.
You make a good point. I’m thinking there would not be military force used nowadays to force a state to stay in the union. We won’t know what would happen if a state tried to secede, until some state actually does so.
It will be interesting to see if secessionist movements gain traction in any states in the years ahead. So far there have not been any serious moves in that direction.