The least important fact about the prospect of Catalonia declaring independence from Spain is that such a declaration would be void under the Spanish constitution. The most important is that Rajoy’s government seems willing to hold Catalonia against its will, and even by force.
It unthinkable that Canada would attempt to hold Quebec captive should it vote to leave the federation. It is unthinkable that the United Kingdom would send in troops to keep control of Scotland or Northern Ireland. Yet neither state has any constitutional provision for regional or national independence. The Canadian federal government, though formally limited in its jurisdiction, has vast powers to invade provincial domains. The Westminster Parliament is unconstrained, and could abolish the Scottish Parliament entirely. It is not any legal difference that explains why neither Canada nor the United Kingdom would behave in such ways. It is a matter of political culture and public morality.
It is true that Canada and the United Kingdom have a deeper and longer loyalty to democracy than does Spain—but that is not the whole story. The larger difference is over another ideal, that of popular sovereignty. It is ultimately for peoples to decide by whom they shall be governed. Popular sovereignty includes the right to make that decision wrongly, and in some cases even to make it in a way that impedes democracy. If Syrians were to freely vote for a theocracy, no other nation should intervene to prevent them.
Some people admit only a thin version of this ideal. They say only colonized or oppressed peoples are entitled to self-determination; everyone else must accept their lot and work within existing law, no matter what. Canadians and the British reject that view. They do not think Quebec or Scotland have the right to decide their futures because they are oppressed by their central governments. On the contrary, they would fiercely deny that proposition and yet still respect the will of the minority nations within their borders.
But what about the rule of law? Must the illegality of any unilateral declaration of independence violate this ideal? The question is more complex than some suppose.
First, if there is any conflict between popular sovereignty and the rule of law we still need decide which should prevail. The idea that existing law should always rule, and be obeyed, no matter what is a repugnant principle. It is one that kept Spain under a dictatorship for years.
Second, and more important, it is not obvious that an unconstitutional declaration of independence on the part of Catalonia would violate the rule of law. To see why, think again about Canada and the United Kingdom. Each not only tolerates but makes possible a lawful route to independence for minority nations.
In Canada, a route to the independence of Quebec is secured by the authority of the 1998 Supreme Court decision in the Reference re Secession of Quebec. The decision did not amend or reinterpret the Canadian constitution. It directed how Canada’s government should respond to any declaration of independence: by good faith negotiation. In the United Kingdom, a lawful route to independence is secured by Parliament’s demonstrated willingness, in Northern Ireland and in Scotland, not only to respect the result of a border poll or an independence referendum, but to provide for, regularize, and recognize such votes. Canada and the UK make possible, and lawful, what Spain leaves to pressure and violence. Spain’s fundamental law renders independence unlawful. It takes a difficult political eventuality for which many countries must somehow provide and puts it beyond the realm of legality.
So is Madrid, not Barcelona, that violates the the rule of law. In denying any lawful route to independence, in disrupting polls, in assaulting voters, and in threatening to remove the regional government of Catalonia, Spain also shows contempt for one of the central ideals of the European Union. And, in refusing to condemn this, the European Union collaborates in an attack on popular sovereignty, and on the rule of law itself.