With the Kurdish referendum in the books and the Catalan vote looming, the question for today is, under what conditions is secession justified? Here are my standards:
1. The geometry has to make sense. It has to be possible to remove the seceding area from the mother country without making the map look ridiculous. Scotland is geographically discrete, so secession there makes sense; Quebec, which is located in the middle of Canada, does not.
2. The seceding area has to have a distinct and separate culture and some history of operating as an independent nation. No elaboration necessary.
3. The seceding area has to have some sort of legitimate historical grievance against the mother country. I say “legitimate” because the case for the Confederacy was based on slavery.
Just because you can meet these standards doesn’t necessarily mean it will happen; the mother country and other affected countries may impose a veto for geopolitical reasons. If you do, however, you meet what I would call the “moral” test, and your claims should be taken seriously.
How do these standards apply to current real world conditions? Kurdistan would meet all of the tests. Quebec would fail #1. Scotland would have a strong case, although you could argue that centuries of cooperation as part of the UK trump the events of the 13th and 14th centuries. The case for Catalonia is debatable on all counts.