Stripping terrorists of their citizenship is tempting for governments and satisfying for voters. It allays concerns that jihadists may recruit and radicalise susceptible inmates while in prison, or that they might one day again roam France and wreak havoc. The symbolism—that a person waging war against France is no longer French—is politically popular: three-quarters of French people support Mr Hollande’s proposal, according to a recent poll.

Yet many on France’s left see it differently. They say that the planned law could foment radicalisation by sending the message to dual-citizen Muslims that they are less French than the rest of society and, by creating unequal categories of citizenship, betray the cherished “egalité” enshrined in France’s constitution. Others squirm at parallels to the Vichy regime’s wartime practice of denationalising French Jews. France would be better off imprisoning terrorists as French citizens than exiling them to failed states such as Syria, free to do damage from afar, critics say. And moves to improve policing and intelligence sharing between European countries would do much more to cut terrorism.

Mr Hollande’s government is not the first to propose such a law. Similar rules came into force last month in Australia; Britain has had much harsher laws since 2013. One country unlikely to see such a law any time soon is America, where it is impossible to be stripped of citizenship unless it was fraudulently acquired. “Citizenship is not a licence that expires upon misbehaviour,” wrote Earl Warren, the chief justice of the US Supreme Court in 1958, “and the deprivation of citizenship is not a weapon that the government may use to express its displeasure at a citizen’s conduct, however reprehensible that conduct may be.”