I just finished listening to the oral argument in Callais. There are almost certainly six votes to rule in favor of Louisiana here. Justice Kavanaugh came to the argument extremely well-prepared, and seems to have mapped out all of the contours of an opinion. It seemed like he was reading from notes, and articulating different standards that could apply. He quibbled a bit with the Deputy SG's phrasing, but I think he is generally comfortable with the government's framing of the case. Chief Justice Roberts was quiet, and (as best as I can recall) only asked whether certain issues were raised in the Alabama litigation a few year ago. The Chief should assign the majority to Justice Kavanaugh, but will probably keep it himself. Justice Barrett was also working out some of the finer nuanced doctrines of the Enforcement Power analysis. She will probably write a concurrence along those lines.
There is much to discuss, but here I want to focus on a broader question of constitutional law.
Section 5 of the Fourteenth Amendment gives Congress the power to enact "appropriate legislation" to enforce the rest of the Fourteenth Amendment. City of Boerne v. Flores Court held that there are limits to Congress's power to remedy a violation of Section 1 (such as the Due Process or Equal Protection Clauses). Specifically, the remedy must be "congruent and proportional" to the constitutional violation.
