Spanish courts have ruled, and leaders have repeated, that the country's Constitution does not allow a region to separate. European Union courts have echoed this position.
Of course, Spain's response to the vote was completely legal. This involved sending police into the region to close polling stations, seize ballots, and deliver some old-fashioned fascist beatings. But it was all to protect democracy, naturally.
The response of the Spanish government is perplexing. They basically strengthened the resolve of the Catalans to remove themselves from an aggressive and violent subjugator. The Spanish government's response was reminiscent of military dictator Francisco Franco's suppression of the Catalan language and culture prior to his death in 1975.
Through their actions to stop the referendum, they showed exactly why Catalonia would want to be independent of Spain.
Further proving the independent nature of the region, Spain had to send in an occupying force to suppress the referendum and attack anyone who tried to vote.
In a sign that Spanish police reinforcements sent to Catalonia might be there for an extended stay, an army logistics unit sent bunkbeds, kitchens and showers to an army barracks near Barcelona in case the police need to use the military base at some point, a Ministry of Defence spokesman said.
Some police staying at hotels in Catalonia have come under pressure from local residents to leave.
Police officers from inside the region of Catalonia would not follow the orders of Madrid.