UNHEALTHILY, the campaign for Crimea's secession referendum, due on March 16th, is more about the vote's legality than its merits. Russia and America are trading hastily concocted arguments over the legitimacy of the republic's probable split with Ukraine. Vladimir Putin insists that "the steps taken by the legitimate leadership of Crimea are based on the norms of international law". Barack Obama, on the other hand, rejects the referendum. "In 2014," he declared on March 6th, "we are well beyond the days when borders can be redrawn over the heads of democratic leaders." Neither Mr Putin's nor Mr Obama's rhetoric fully accounts for the competing norms at play. International law does not recognise a right to secede per se, but it also steers clear of prohibiting unilateral declarations of independence. International legal bodies regard the result of successful break-ups the way friends see a separating couple: as two newly unlinked individuals, like it or not. So if Russian-speakers in Crimea (which already has the status as an "autonomous republic") vote to slice themselves off from Ukraine next week and throw themselves into the arms of the Russian Federation, no international court will raise much of a fuss—but neither would one take pains to defend the peninsula's right to secede.

Ukraine, in contrast, has cause to reject the legality of its dismemberment at the hands of the people of Crimea. Article 73 of the Ukrainian Constitution is unequivocal: "Alterations to the territory of Ukraine shall be resolved exclusively by the All-Ukrainian referendum." Crimea is not allowing the rest of Ukraine's 44m people to weigh in on the fate of the peninsula, so the March 16th vote will violate Ukrainian law. Secession movements, though, do sometimes proceed without the permission of the mother country. America's fight for independence was an illegal war of secession against Britain. In 2008, under the modern international legal regime, Kosovo's split from Serbia did not have the backing of the government in Belgrade, nor that of dozens of other states. Yet it was recognised by a large majority of UN member countries. Russia compares Crimea to Kosovo, accusing the West of double standards. America says the two are different and levels its own charge of hypocrisy: Russia violently quashes self-determination for Chechnya, for instance, while championing the secession rights of Crimeans. Should Crimea vote to become part of Russia, it is likely to be the subject of exceptions and carve-outs in future treaties between Russia and those countries that do not recognise the territory's secession.

Beyond the question of legality, does Crimea have a right to quit Ukraine? Allen Buchanan, a political philosopher at Duke University, argues that provinces might justify seceding if they are discriminated against. The Basque separatists portray their plight with the image of a cow: its mouth feeds in Basque territory while its udder rewards those living elsewhere in Spain. But claims that Russian-speakers in Crimea face violence and oppression from Ukrainian fascists are preposterous. Indeed, by some accounts, Ukraine subsidises Crimea and stands to gain economically from secession. So does Ukraine have a right to force Crimea to stay? Mr Buchanan thinks it would, if the break-up would gravely harm the mother country. Look at a map, though, and you'll see that Crimea resembles an anvil tenuously attached to the rest of Ukraine by a thread. Although Crimea provides access to the Black Sea and brings in tourist money as well as some industry and agriculture, the loss of 4% of the population would hardly count as a devastating economic blow to Ukraine. The referendum has been arranged at ten days' notice, it does not offer voters the status quo—just secession or absorption by Russia, and it is being held when Crimea is occupied by Russian elite troops. However you judge the referendum's legal niceties, what counts is that it is unfair and that it sets a terrible precedent.

Dig deeper:

Having occupied Crimea, Russia is stirring up trouble in eastern Ukraine (March 2014)

President Obama is bad at alliances with allies, but the crisis in Ukraine predates him (March 2014)

Why the occupation of Crimea should be punished (March 2014)

Correction: This post originally said that Russia quashed self-determination movements in "Chechnya, Georgia, Moldova and Azerbaijan". As several readers pointed out, Russia has thwarted self-determination for Chechnyans but has supported it for groups in the latter three places. The post has been amended.