The takeaway When it comes to the status of their foreign labour, the Gulf and Arizona actually represent the extremities of two very different paradigms of immigration.
Models of migration: Arabia versus Arizona
It's not uncommon for American visitors to the Gulf to say that the cities here remind them of Phoenix, Arizona - another young desert metropolis rich with golf courses, car culture, palm trees and foreign labour. But when it comes to the status of that foreign labour, the Gulf and Arizona actually represent the extremities of two very different paradigms of immigration. One - the Gulf paradigm - makes it easy for large numbers of unskilled workers to migrate in but does not afford them a pathway to citizenship, making employers the arbiters of their residency. The Euro-American paradigm, by contrast, preserves legal immigration as a route to full citizenship and a guarantee of (mostly) equal rights, but sets tight controls on the volume of those allowed in, inadvertently and inevitably producing vast flows of illegal migrants.
Late last month, Arizona emerged as a corrosive breaking point for the American model. The south-western border state passed a hugely controversial law requiring police to demand proof of legal residency from anyone who arouses the "reasonable suspicion" that he or she might be an undocumented worker; the law also commands police to arrest anyone who cannot - like one of those poor extras in Casablanca - produce their papers.
The immigration bill washed up in a tide of nativist flotsam: the state's department of education has recently directed schools to dismiss teachers who speak in heavy accents or without perfect grammar from classrooms where English is the language of instruction. Another nearly-successful bill would have required any American presidential candidate campaigning in Arizona to produce a birth certificate - a nod to the "birther" conspiracy theorists who suspect Barack Obama isn't really American.
The issue of immigration has been simmering in the background of American politics for years; Arizona's legislative spree may signal its eruption into full boil. Radio talk show hosts in Texas are already suggesting that the new law will drive illegal immigrants out of Arizona and into neighbouring states - and that Texas should pass its own similarly tough anti-immigration law to fend off the onslaught. A nationwide poll by the Gallup organisation found the new Arizona law popular with 51 per cent of Americans who had heard of it.
Meanwhile, 30 per cent of people living in Arizona are of Latino origin, and their cause for anger and anxiety is clear. "If you're brown-skinned, and don't have your wallet, you're going to jail," wrote William Finnegan of The New Yorker. The danger, in other words, is that the contradictions and political upheavals of a system that breeds widespread illegal immigration are spilling over to affect the lives of legal immigrants.
The American paradigm of immigration is breaking down. But the Gulf paradigm is unpalatable to both liberals and conservatives in western democracies. Conservatives see the Gulf's approach as one that is bound to overrun the homeland with foreigners, and liberals see it as a policy bound to leave migrants vulnerable to exploitation and the public morally coarsened by a regime of legal inequality.
But the deepest and cruelest form of inequality - the one imposed by the accidents of geography and the imaginary outlines we call states - persists. As long as it does, the huge wage differentials between nations will drive migrants to risk their lives traversing them. Just as nature abhors a vacuum, labour abhors borders. Attempts to defy this reality, however energetic or harsh, will continue to fail.