Should states/regions etc. have a right to secede from their nation-states?

[Mr. Reactionary]

Pretty much, with the caveat that it is the people making up the state who have the right. Of course there would need to be an adequate system for determining the will of the people (Both a referendum and a vote in the legislature). There would need to be a mechanism for resolving issues of government property and dual citizenship as well. For example, at the onset of the Civil War a delegation representing the Confederacy offered to pay the U.S. for the value of military bases and other government buildings and improvements in the south, as well as an apportioned percent of the existing national debt. When the Soviet Union dissolved, Russia offered a certain type of dual citizenship to residents, and gave them the option to reject Russian citizenship. In the U.S., this would be a necessity to deal with the 14th Amendment issues (and potential 5th Amendment one as well).

But in principle, I agree with Abraham Lincoln's view that:  "Any people anywhere, being inclined and having the power, have the right to rise up, and shake off the existing government, and form a new one that suits them better. This is a most valuable - a most sacred right - a right, which we hope and believe, is to liberate the world. Nor is this right confined to cases in which the whole people of an existing government may choose to exercise it. Any portion of such people, that can, may revolutionize, and make their own of so much of the territory as they inhabit.”