Liberal nationalism is a contradiction in terms. The world doesn’t divide up neatly into nations, each of which can live happily within its own state. The notion of self-determination does not deal with the hard cases. In 1939, the spark of war was the clash between the self-determination of Poland as against the self-determination of Danzig.
The whole point of supranational institutions and regional integration around the world is to provide guarantees to those people who might otherwise think of themselves as living in the “wrong” country. When being on the wrong side of a border is a matter of life and death, it is not surprising that people fight. Better to make redundant the whole notion. Democracy and human rights should take the place of self-determination.
What weasel words, “other things being equal”! In an interdependent and ethnically mixed world, other things never are equal and never can be. To found a political doctrine on the basis of what ought to be rather than what is, is the last thing one would expect from the Conservatives.