The Arizona law -- Proposition 200 -- sets out the acceptable documents. The law says you can us the number of your naturalization certificate, which of course you have right to hand. You fill it in and send off the new form.

Soon comes another letter. "Let this letter serve as notification that ..." Well, naturalization certificate numbers, it turns out, aren't stored in a database where county officials can use them, so despite what the law says, they aren't accepted. You can't mail in a copy, because it's illegal to photocopy one. The only way to register, it turns out, is to go to the courthouse and present the certificate in person. Nowhere on your federal form was there a warning that your driver's license and naturalization certificate numbers would be rejected.

Here's a question: Did state officials "accept and use" the federal form? Of course, says the state of Arizona. They allowed you to mail it in -- acceptance -- and read it so they could reject your application -- use. After all, they say, employers "accept and use" job applications; they just reject most of them.

No, say a group of Arizona voters and voter advocacy organizations; it is the clear intent of the NVRA that a completed form should provide all the information the state needs. It can check the information against public records to determine citizenship. It can send a letter announcing your registration, and then suspend if the letter is returned as undeliverable. What it can't do is make the voter jump through more hoops than the form requires.

At oral argument Monday in the U.S. Supreme Court, it seemed as if the result might turn on fine parsing of the words "accept and use." But lurking behind the statutory argument was another, more unusual one: at least four of the justices made it clear that they thought they could design a better form.

The textual power at issue in Monday's case, Arizona v. Arizona Inter-Tribal Commission, is granted in Article I § 4 of the Constitution:

The Times, Places and Manner of holding Elections for Senators and Representatives, shall be prescribed in each State by the Legislature thereof; but the Congress may at any time by Law make or alter such Regulations, except as to the Place of Choosing Senators.

The NVRA, or "motor-voter" bill, is an exercise of the "make or alter" power. In 1993, Congress determined that many states made it too hard to register. They empowered a federal agency to design a form -- and said that the form "may only" ask about certain things, such as age, address, and citizenship. Then they said all states are required to "use and accept the form."

Flash forward to 2004. Voters in Arizona became concerned that illegal aliens were flocking to the polls. They enacted Proposition 200, which requires the state to reject any form not accompanied by "satisfactory evidence of citizenship" -- a class of documents rather whimsically defined, as the naturalization-certificate-number snafu illustrates.