That is the topic of my latest Bloomberg column, here is one excerpt:
When an empire is crumbling, and the rulers are very bad, the libertarian approach to secession makes good sense. That said, it’s not a fully general principle.
Sometimes a region wants to leave a country because of differences of ethnicity, religion, language or background culture, as is the case with the Scottish independence movement and the Catalonian secessionists. In those instances, it’s not obvious whether a unified or a newly independent government would result in greater liberty and prosperity. And for all the strong feelings you will find, I am not sure there is an objectively correct moral answer as to whether there should be one nation or two.
We do know, however, that political tensions rise and emotions tend to flare as such secessions approach the realm of possibility. For instance, there is a chance the government of Spain would react aggressively to what it perceives as an unconstitutional Catalonian secessionist attempt. Madrid might institute legal sanctions against Catalonian leaders or, in an extreme case, send in troops. The final result could be no independence and less liberty in all parts of Spain.
The problem is that people are often overly passionate about political boundaries, and an extra dose of irrationality isn’t exactly what the world needs right now. To cite another example of this problem, the Brexit referendum seems to have lowered the quality of debate and governance within the U.K.
There is much more at the link, including a discussion of why the American Revolution might have nonetheless been a good idea, and also why the libertarian approach needs to be supplemented with conservative ideas.