In Operation Anubis, the Spanish police attempted in various ways to stop the Catalan independence referendum, 2017 from taking place.
I don't understand why the bother. The Spanish constitutional court has declared the referendum unconstitutional. The Spanish state can simply declare that the voting has no legal force, like they did for the 2014 referendum. What does the Spanish state achieve by attempting to block people from voting in a poll that they do not recognise in the first place?
