"So it's under oath. Big deal." That's not exactly the sort of statement you'd expect from a sitting Supreme Court justice, but here we are.

"Big deal," Justice Antonin Scalia scoffed, during today's arguments concerning Arizona Proposition 200, which mandates proof of citizenship for residents filling out a federal voter registration form. The federal government includes a space on the form for an applicant to indicate that he is a citizen, to swear to it by affirming his signature. "Big deal," says Scalia.

Or, more specifically, Scalia said:

[I]t seems to me you were quite able to argue that in — in refusing to allow you to include in the — in the Federal form in Arizona some indication of proof of citizenship requiring nothing else except oh, I'm a — check off, I am a citizen, right? So it's under oath. Big deal. If — if — if you're willing to violate the voting laws, I suppose you're willing to violate the perjury laws.

Which is a nifty little bit of argument, for a few reasons. First, that it is basically an argument against any law. Why have a law, if the person will just break it? Why require proof of citizenship — which, under Proposition 200, means providing a passport or birth certificate — when people could just forge their documents? And, second, there's this, as presented by the plaintiffs' attorney, Patricia Millett.

JUSTICE SCALIA: … [T]he Commission has – has required its — its own proof and the State wants a different kind of proof. The proof the Commission requires is simply the statement, I'm a citizen. This is proof?

MS. MILLETT: This is — statements –

JUSTICE SCALIA: This is not proof at all.

MS. MILLETT: Statements under oath, statements under oath in a criminal case –

JUSTICE SCALIA: Under oath is not proof at all. It's just a statement.

MS. MILLETT: Statements under oath in a criminal case are proof beyond a reasonable doubt by which we execute them. … It's a very serious oath.

And that seems like a pretty solid argument. The American legal system is largely predicated on sworn testimony, either oral or written. Every day, juries are asked to consider sworn testimony — some of it from perjurers, to be sure! — and evaluate the guilt or innocence of a defendant. What else could we do?

And, of course, those documents that the state of Arizona insists be presented are themselves sworn documents: a passport requires any applicant attest to the truth of a submitted application. But someone planning on committing voter fraud could just violate that law, too.

An important caveat: the quotes above come from the Supreme Court's official transcript of the proceedings, undoubtedly transcribed by a court stenographer who swore an oath to represent the proceedings fairly. Big deal. Probably made the whole thing up.