The last Catalan leader to try to proclaim the existence of a Catalan state, Lluis Companys, did so in October 1934, 80 years ago this year, against: “monarchist and fascist forces who mean to betray the Republic”. It was, he said: “a grave and glorious hour” for Catalans.

The Spanish prime minister at the time, Lerroux, ordered the Captain General of Catalonia, Batet, to declare a state of war in the region and quash the rebellion, which he did with his edict. His forces surrounded the Catalan government building, the Generalitat, and stormed it. Artillery pieces and machine guns were brought out onto the streets of Barcelona, and 46 people were killed.

That version of Catalonia lasted just ten or eleven hours after the Mossos, the Catalan police force, surrendered to the Spanish Army and Civil Guard. Companys and the members of his government were all arrested and imprisoned initially on a boat called the Uruguay to await trial. The Catalan parliament was closed, a civil governor appointed by Madrid and the Catalan Statute revoked.

Companys and his ministers were sentenced to 30 years in jail for the crime of rebellion, but were pardoned after the Popular Front won the general elections in February 1936, five months before the start of the Civil War.

Contemporary supporters of the independence of Catalonia insist that violent confrontation is not and never will be part of their secession narrative or activities and hope that Madrid will somehow just hand over the keys to the castell if they can achieve some kind of majority in a vote that, in Madrid’s eyes, will always be illegal.

But the crime of rebellion still exists in the 1995 Spanish criminal code. Article 472.5 is quite clear that the legal definition of rebellion includes: “declaring the independence of a part of the national territory”, and article 476 is very specific about the legal duty of Spanish military officers to use “the means at their disposal” to quash any attempt at rebellion “in forces under their orders”.

The longest jail sentences the leaders of such a rebellion could expect to receive nowadays are not very far short of those handed down to Mr. Companys and his ministers: 15 to 25 years in prison.

Observers may add these legal notes to Mr. Rajoy’s constitutional defence of the rejection of any vote on a referendum, the overwhelming parliamentary vote against the request in April, and this week’s declarations by Pedro Sánchez, the new leader of the Spanish Socialist Party (PSOE), who said the consultation could not take place because it is illegal.

For the past two years, since Diada Day in 2012 and Mr. Mas’s meeting with Mr. Rajoy shortly thereafter, Spaniards have expended much time and energy contemplating the different future outcomes for the Catalan question.

Politically, Mr. Rajoy and the governing Popular Party have been unwise to employ the arrogance and contempt they have shown towards supporters of Catalan independence, whilst Mr. Mas and Catalan politicians have spent two years egging on Catalan voters with dreams of peacefully and democratically redrawing the map of Spain for the first time in 300 years.

The balance of most forms of real power—legal, political, police, military, etc—currently weighs in Mr. Rajoy’s favour. Independence fans claim social power and majority citizen support for a vote on secession but Catalan voices against secession have grown in number of late, and unless supporters of independence are willing to actually fight against those other forms of real power in some more rebellious way, it is difficult to see how they can win any extra-legal political conflict.

The economic question is more of a double-edge sword. The stakes are massive, 19% of Spanish GDP and 26% of Spanish exports, contagion in the Basque Country—but the very size of the Catalan economy means it is systemically important within Spain, as is Spain within Europe. Mr. Junqueras, the leader of Catalan Republican Left (ERC), hinted at this way of raising the stakes in global financial markets in a recent interview with Bloomberg.

No one knows how this will play out, if Mr. Mas will succeed in holding the Catalan vote on November 9, or whether Mr. Rajoy will attempt to enforce Spanish law slightly more energetically over the coming months, but the closer Spain gets to that autumn day, the more the complexities of the real world will take us deeper into unknown and unknowable political territory in Spain, and all of the scenarios will unfold within today’s highly-connected, high-speed 21st-Century world.

What happens when Mr. Rajoy orders the Civil Guard to uphold the law in Catalonia and Mr. Mas orders the Mossos to defend his government’s position? Bond yields could begin to spike quite dramatically towards the start of November.