In reviewing the Supreme Court oral argument in United States v. Barbara, in which the justices considered the lawfulness of President Trump's anti-birthright-citizenship Executive Order, I was struck by an exchange in which a fairly obvious question seemed to catch the SG off guard.

Justice Kavanaugh asked the Solicitor General about the extent to which Congress might have authority to modify the contours of birthright citizenship, and the SG's response suggested he had never pondered this question before.  Here is the transcript of exchange:

JUSTICE KAVANAUGH: Of what relevance, if any, do you think Section 5 of the Fourteenth Amendment has here that gives Congress the power to enforce the article, the Fourteenth Amendment, by appropriate  legislation? Does that give Congress room here, or do you not think so?

GENERAL SAUER: I --I do think that a ruling in our favor would leave room for Congress. I --I don't think you have to rely on Section 5. I think that Congress has its own inherent power to grant citizenship by statute. So, if the Court were to rule in our favor for the classes of individuals that they say should be covered, Congress has the latitude to do that.

JUSTICE KAVANAUGH: How much room do you think Section 5 gives, if any --and it may not be any --Congress to interpret the phrase "subject to the jurisdiction thereof" or to define that? Does it --is that --is that relevant at all?

GENERAL SAUER: It's a great question, and I'm thinking about it for the first time. I assume it would be governed by the congruence and proportionality test from this Court's case law. How that would apply here, I don't know. And I don't think it's presented because our contention is that the statute means exactly the same thing. If anything is congruent and proportional, it's that. And I think the Court held that in United States against Georgia.

I understand that the SG is trying to defend the Executive Order, and it is quite unlikely that Congress is going to enact legislation on birthright citizenship any time soon, but I was nonetheless quite struck to hear the SG confess he had not previously considered the extent to which Congress might have the power to define who is "subject to the jurisdiction" of the United States for purposes of birthright citizenship, as this would seem to be quite relevant to the legal issues in play.

I previously blogged on the oral argument in Barbara here.

The post The Birthright Citizenship Question that Stumped the Solicitor General appeared first on Reason.com.