Even more ironically, a case could be made that that very European Union has already dissolved the Scots’ Union with England. For in the Union with Scotland Act of 1706, the Scottish people decided to share a sovereign and a parliament.
Since the new parliament of the United Kingdom was to be in England (and the physical existence of the Scottish parliament dispensed with) the terms of the Act of Union were absolutely vital. The Scots, effectively, gave up their parliament only in return for the guarantee that the new (English dominated) parliament would not curtail or in any way diminish their rights. If they did so (as has now happened under various EU treaties), then the Act of Union would be null and void and not only would the United Kingdom cease to exist, but so would the authority of the parliament at Westminster, which was spawned by the Act of Union. That is the situation today. So we have two parliaments with no power holding a referendum over a union which does not exist.
Meadowfield Road Stocksfield, Northumberland