Some might think that the fight for universal suffrage was won a long time ago, but in many parts of the supposedly democratic world there are still constant attempts to make voting more difficult for the poor, the young, immigrants and the itinerant. Not coincidentally, all those groups have a tendency to vote for parties of the left, and the attempts to wind back their rights usually (although not invariably) come from the right.

One such attempt was knocked on the head yesterday by the US Supreme Court in the case of Arizona v. Inter Tribal Council of Arizona Inc. You can read the full judgement here, or the BBC report here (credit to the BBC for actually providing a link).

As most readers will be aware, electoral law in the United States is a patchwork of mostly state and local rules. But a Clinton-era federal law, the National Voter Registration Act of 1993, requires states to accept enrolment (called “registration”) by means of a standard federal form, which can be lodged by mail. Arizona, however, had legislated (under a 2004 referendum) to require people to produce proof of citizenship when enrolling, which effectively ruled out the option of doing it by mail.

By a 7-2 majority, the Supreme Court ruled that this was a simple case of conflict between state and federal law, and the federal law prevailed. Interestingly, Antonin Scalia, the intellectual leader of the court’s conservative wing, wrote the majority judgement; he was joined by chief justice Roberts and the liberal bloc of justices Breyer, Ginsburg, Kagan and Sotomayor, plus the swing vote of justice Kennedy. Conservative justices Alito and Thomas dissented.

It’s not quite the triumph for voting rights that it might seem: the court emphasised that federal power extended only to the mechanics of enrolment, not to actual qualifications to vote, which remain a state responsibility. The federal law allows additional requirements to be added to the standard form at a state’s request to ensure that that state can properly check an applicant’s eligibility. In 2005, the federal Election Assistance Commission declined (on a tied vote) to act on Arizona’s request to do so in this case; the state failed to seek judicial review of that decision. Scalia suggested that it should.

There are still plenty of ways states can make things difficult for would-be voters that this decision doesn’t touch – particularly laws requiring the production of identification when voting, which are still being litigated in many states. But it’s at least a step forward, and shows the Supreme Court willing to intervene against restrictive state laws.

There’s an element of consistency there for Scalia and Kennedy, who both voted to comprehensively trash state autonomy over electoral matters in 2000’s Bush v. Gore. How Justice Thomas, on the other hand, manages to reconcile his dissent in the present case with his vote in Bush v. Gore is anyone’s guess.

It’s also interesting to note the way Scalia’s legendary arrogance is quite capable of being trained against his fellow conservatives instead of his usual liberal targets. In particular, don’t miss his footnotes, which provide a running and generally unflattering commentary on the dissenting judgements.