The question of whether Spain has the right to shut down Catalonia's independence referendum is a complex and controversial issue that is subject to different interpretations and opinions.
From a legal perspective, the Spanish Constitution, which was adopted in 1978, recognizes Spain as a "nation with a single sovereignty" and prohibits any attempt to secede or break away from the country's territorial unity. Therefore, according to the Spanish government, any attempt by Catalonia to hold an independence referendum would be unconstitutional and illegal.
In 2017, the Spanish government declared the Catalan independence referendum to be illegal and took measures to prevent it from taking place. This led to clashes between protesters and police, and the Spanish government's imposition of direct rule over Catalonia for a period of time.
Supporters of Catalonia's independence argue that they have the right to hold a referendum under international law and fundamental human rights principles, including the right to self-determination. They claim that the Spanish government's refusal to allow a referendum is undemocratic and violates the Catalan people's right to decide their own future.
Ultimately, the question of whether Spain has the right to shut down Catalonia's independence referendum is a matter of interpretation and perspective, and there are valid arguments on both sides. It is a complex issue that requires careful consideration of legal, political, and social factors.