For the past week, France has felt like a country on the verge of civic insurrection. Union blockades of petrol refineries and depots have caused widespread fuel shortages. Some 2,300 petrol stations have either run dry, or are rationing sales at the pump. The government has dipped into its strategic reserves to maintain supplies. Panic has created shortages, as motorists queue to fill up their tanks. The showdown is fast turning into a battle over the survival of both the Socialist government and the reformist French left.

The strikes have touched not only the petrol industry. The Confédération Générale du Travail (CGT), France’s biggest union, which is historically close to the Communist Party, has organised protests and walkouts for the past few months on the railways and Paris metro, as well as French nuclear-energy plants. Riot police have been dispatched to clear illegally blocked fuel depots, most of which have now been freed. Daily images of tear gas and police water cannons, burning tyres and serious street violence—rioters hurled a petrol bomb into a police car while two officers were still inside (see video below)—have dominated the news.

The immediate gripe is a modest liberalisation of labour laws. Weeks of discussion in parliament and protests on the streets had prompted the government to water down its more radical provisions. The final version will, nonetheless, make it easier for firms to negotiate working time and pay directly with their employees, and ease some rules on redundancies—part of an effort to encourage job creation in a country where unemployment is stuck at 10%. Despite the concessions, however, a parliamentary rebellion by a Socialist minority earlier this month threatened to defeat the bill. Manuel Valls, the centre-left prime minister, keen to show that he would not cede to his party’s left, decided instead to push the bill through the National Assembly with an express procedure—without a vote on the law itself but subject to a vote of no-confidence in the government as a whole.

Far from securing Mr Valls the image of decisive leadership, this decision has provoked a double hostility. First, the substance of the bill is seen by the CGT and Socialist rebels as an assault on workers’ rights. Philippe Martinez, the CGT’s leader, who is forging his reputation on the strikes, called it a “return to the 19th century”. Second, the government’s use of an article in the constitution to bypass parliament has led to accusations of anti-democratic behaviour. “It’s a form of brutality, a denial of democracy,” said Laurent Baumel, a Socialist rebel.

Despite the hours of parliamentary debate and all the amendments agreed, public opinion seems to agree with Mr Martinez, not Mr Valls. Fully 62% told a poll that they thought the CGT-led strikes were justified. In another poll 70% said the law should be shelved in order to end the blockades. The government has accused the CGT of holding the country hostage. Le Monde and other papers said that the union had refused to print their newspapers this week because the editors had declined to run an anti-labour-law tract written by Mr Martinez. Yet motorists have displayed unusual calm while waiting in queues. “What choice do we have?” shrugs one, playing on his iPhone with his car’s engine off in a half-hour queue in a Paris suburb.

Neither side looks ready to back down. Mr Valls and the president, François Hollande, have hinted that some modifications might yet be possible, but vow not to give in on the bill. Mr Hollande, with approval ratings of just 13%, is already weak. And the pair can ill afford another embarrassing climb-down: earlier this year they went through the fiasco of shelving a different, controversial, citizenship bill. For his part, Mr Martinez, a former technician at Renault, was elected only last year, and has a reputation to build. The CGT has been weakened in recent years, and he badly needs a muscular demonstration of force to make his mark.

The outcome could be decisive for the future of the French left. If the government stands firm and the centre-left ground is reinforced around the more centrist Mr Valls, the left-wing could conceivably split away. “The rebels are against everything, on principle,” says a minister, who predicts such a fracture. Yet this will be difficult to achieve unless public opinion shifts. If, on the other hand, the Socialist rebels and the CGT get their way, the government’s survival will be in the balance and the battle for control of the left becomes wide open. Even if some sort of compromise is found, the centre-left’s credibility could still be badly undermined.

Perhaps the most critical lesson is the importance of political legitimacy. Mr Martinez’s economics may be daft and damaging. Yet when he accuses Mr Hollande of implementing a programme for which he was not elected, he is partly right. In 2012, as the Socialist candidate, he promised to fight high finance, end austerity and squeeze the rich, not to loosen the labour code. Unlike Mr Hollande, Mr Valls has at least long made the case for a more centre-leaning policy. Yet he has no direct mandate for such reform either. France is a volatile place, with a romantic sympathy for resistance and long tradition of street theatre. Not, in short, a country easy to steer in one direction when, like Mr Hollande, you are elected to go in another.

This article originally appeared in The Economist.