There is one important difference: The "Brexit" has a legal foundation in the Treaty of Lisbon that sets out a mechanism, the infamous article 50 (written by a

There is one important difference: The "Brexit" has a legal foundation in the Treaty of Lisbon that sets out a mechanism, the infamous article 50 (written by a Brit, it transpires). Similarly, the independence referendum in Scotland had a legal foundation, an Order in Council. The division of Czechoslovakia was done by making constitutional law. Catalonian independence has no such legal foundation to rely upon, albeit that constitutional reforms aimed at providing one have been attempted. The U.S. constitution lacks a secession mechanism, too, some of the consequences of which are well known.