Associated Press
As an uncharacteristically united Supreme Court wisely decided this week, states do not have the authority to override federal law.

As Congress continues to drag its feet in crafting workable immigration reform, it's understandable that some states have tried to come up with solutions of their own. But as an uncharacteristically united Supreme Court wisely decided this week, states do not have the authority to override federal law.

Arizona's law requiring proof of citizenship when registering to vote in federal elections was overturned by a lopsided 7-2 majority. "No matter what procedural hurdles a state's own form imposes, the federal form guarantees that a simple means of registering to vote in federal elections will be available," Justice Antonin Scalia wrote on behalf of himself and the six other justices who voted with him to strike down the law.

Simplifying the law was one of the purposes of the 1993 Motor Voter Act, which requires all states to "accept and use" the simple federal form in registering voters for federal elections. This is a form that already requires voters to state, under penalty of perjury, whether or not they are citizens of the United States. Arizona's additional requirements would have unnecessarily complicated the registration process for all voters in a way that violated the intent of the original legislation.

Procedurally, this prevents states from cluttering up the federal voter registration process to accomplish goals with no direct relation to federal elections. This is not to say that it's acceptable having non-citizens in the voting booth, but rather that the voter registration process is not a mechanism designed to enforce immigration laws. In addition, if the Supreme Court had upheld the law, it would have opened the door to any number of abuses and established a precedent that states are not required to obey federal requirements they don't like.

In addition, the law is superfluous in light of Arizona's Voter ID requirement that mandates all voters show valid identification, such as a driver's license, when they show up at the polls. So why demand ID at the time of registration, too?

Some unhappy with the decision have called for the federal government to take action to modify the law as it exists. Texas Sen. Ted Cruz has already drafted an amendment that would allow states to do what Arizona was attempting to do. That would make for bad policy, but at least it would be following the proper procedure. Immigration is a federal issue, and so is registering to vote in federal elections. States, even when they have the best of intentions, are not exempt from following federal law.