Arguments about Islam are liable to generate more heat than light wherever they take place, but one of the unlikelier hotspots over the last year was the state of Oklahoma. In 2010, a group of its Republican lawmakers proposed that local courts be forbidden from taking account of the sharia, and 70 per cent of voters backed a draft constitutional amendment to that effect. The law, known to supporters as the ‘Save our State’ amendment, was justified as a ‘pre-emptive strike’ against an imminent ‘onslaught’. Similar initiatives were soon spawning elsewhere, and by late 2011 they had been tabled in 24 legislatures, from Alabama to Wyoming.

On 10 January, however, three federal judges ruled on a challenge brought by Muneer Awad – one of the 30,000 or so Muslims in Oklahoma (population 3,751,351) – and found that the amendment violated the US constitution. Its provisions, they held, fell foul of the principle that governments must avoid excessive entanglement with religion. And though their decision directly affects Oklahoma alone, it all but confirms that the other pending bills are unconstitutional.

The unanimous opinion could hardly have been more forthright. The court roundly rejected a claim that the amendment had caused the plaintiff no legal harm, and gave short shrift to an attempt to portray the measure as a religiously neutral regulation. Instead, the judges found it to be overtly discriminatory, which meant that its defenders had to prove a ‘compelling state interest’ for its enactment – and they couldn’t.

[They] do not identify any actual problem the challenged amendment seeks to solve. Indeed, they admitted... that they did not know of even a single instance where an Oklahoma court had applied Sharia law... let alone that such applications or uses had resulted in concrete problems in Oklahoma.

The rise and fall of the Save our State amendment illustrates the continuing potency of anti-Islamic sentiment in the United States. In the name of confronting a scenario that was palpably fantastic, Oklahoma legislators were able to galvanise more than two-thirds of voters to cast ballots against the presumed interests of a minuscule and law-abiding religious minority. Their success then unleashed similarly intolerant campaigns across the nation, all of which drew on a vague sense that US Muslims were somehow in cahoots with the nation’s post-9/11 enemies. And yet, at the same time, the appeal court decision illustrates that the prejudice has very definite limits: the risk of electorally sanctioned repression was reined in by a reassertion of straightforwardly secular constitutional principles.

Perhaps most important, the ruling is a reminder that hostility to ‘the sharia’ is not the same as opposition to extremist Muslims. To the devout, the word has otherworldly connotations – originally a term used by desert Arabs to describe a path to water, it means the route towards eternal salvation – and its precepts are as extensive as that suggests. They guide a believer from cradle to grave: one of Awad’s complaints about the Save our State amendment was that it might stop a probate judge from acknowledging references to the sharia in his will. The fact that Muslims profess to believe in a path ordained by God bears no significant relation to the practical risks posed by extremism. Anyone genuinely concerned by those risks ought to challenge specific interpretations of Islamic law that lead to acts of violence or injustice, not every expression of religious belief that Muslims call ‘the sharia’.

This is as true in the United Kingdom as it is in the US. Opposition to the sharia has become increasingly common here in recent years, and though its opponents think their repugnance is rational, the animosity has a very dark side. Just as some American conservatives have been nudged since 9/11 towards an undifferentiated credophobia, anger at Muslim extremists has poisoned debate in Britain and promoted a generalised contempt towards Islam. The US court’s decision is a robust affirmation that the American constitution does not need institutionalised discrimination to survive. Anyone who feels instinctively opposed to the sharia, assuming it to be a reflection of their own worst fears, could usefully take note.