A Supreme Court ruling this week confirmed federal supremacy over U.S. voter-registration procedures, yet it didn't challenge the power of states to set the basic qualifications for being able to vote. Justice Antonin Scalia's majority opinion in Arizona v. Inter Tribal Council of Arizona was as much a reaffirmation of state prerogatives over access to the ballot box as it was of federal power to determine the procedures.

These rules overwhelmingly demand that voters have citizenship. But why should that be the case? Citizenship hasn't always been a requirement to vote in the United States. Nor should it be in the future. The Constitution bars discrimination by states on the basis of race, gender and age. It is mute on citizenship.

The New York City Council is seriously considering a measure that would permit voting by legal-resident noncitizens in municipal elections after six months' residence. If the measure passes, it would surely energize similar initiatives in other major metropolitan areas.

Noncitizen voting was once the norm, even in federal elections. At the beginning of the 20th century, as many as 22 states and territories allowed noncitizens to vote not just for local but also for national elections. Noncitizens legally voted in every presidential election until 1924. The practice coincided with an immigrant surge approximating today's.

Noncitizen voting in local elections is becoming a global commonplace. European Union member states are required under the 1993 Maastricht Treaty to extend the local franchise to those who relocate from other member states. Many European countries (including Belgium, Spain and Sweden) allow noncitizen voting in local elections by immigrants from outside the EU, as well.

Britain allows resident citizens of Ireland and the Commonwealth nations to vote in parliamentary elections. In Portugal, citizens of Brazil can participate in national elections. New Zealand and Chile allow permanent residents, regardless of origin, to vote in national and local elections.

In the U.S. today, Takoma Park, Md., remains the only locality in which noncitizens can vote in local elections. Recent ballot referendums to allow noncitizen voting have been narrowly defeated in San Francisco and Portland, Maine.

The New York measure has the support of a majority of members of the City Council. The legislation has drawn fire, predictably from restrictionists on the right and more surprisingly from pro-immigrant progressives and New York Mayor Michael Bloomberg.

Opponents of noncitizen voting ignore basic conceptions of self-governance. Noncitizens are directly affected by local government and pay local taxes. Accordingly, they should have the same say as their neighbors in how they are governed. Nationally, most immigrants are subject to a five-year residency requirement before they can become citizens. By contrast, a U.S. citizen who moves from Alabama to New York is eligible to vote only 30 days later. Nationalists respond that noncitizens can have their vote - they just have to naturalize to get it. Yet not every noncitizen is eligible.

For those who are eligible, the hassle and expense of naturalization shouldn't be an obstacle to local political participation. Our contemporary constitutional sensibilities are repelled by the old poll taxes and literacy tests of our segregated past. Unfortunately, a citizenship qualification for the local franchise imposes similar barriers for a new class of mostly disempowered residents.

What liberal opponents of noncitizen voting seem to be missing is that it would serve their agenda by getting immigrants politically engaged. They should think of it as a gateway right. Once immigrants become more involved at the local level, they will have a greater incentive to seek admission to the national polity.

Some immigrants could naturalize but don't want to because they don't identify as Americans. But they might still identify as Portlanders, Washingtonians or Angelenos.

Local citizenship, local voting: an idea that even Scalia can live with.

Peter Spiro is the Charles Weiner professor of law at Temple University's Beasley School of Law. He is a former law clerk to Justice David Souter of the U.S. Supreme Court.