The judgment in 'Morales-Santana' (and a Supreme Court symposium)

[I meant to mention this earlier, but for the month of June—i.e. Supreme Court "high season"—I will be participating in an online symposium over at Prawfsblawg, along with a bunch of great guest-bloggers: Steve Sachs, Ian Samuel, Dan Epps, Chris Walker and Leah Litman, as well as the permanent bloggers at Prawfs. I will generally cross-post my own contributions here, but if you want to follow the whole conversation, you can read all of the posts here. And with that, here's my most recent post, on Monday's decision in Sessions v. Morales-Santana:]

Howard Wasserman and Ian Samuel have both posted about Monday's opinion in Sessions v. Morales-Santana, in which the court held Section 309(c) of the INA unconstitutionally discriminatory, but then held that the remedy was to apply the stricter rule across the board ("leveling down," or what Samuel calls "the mean remedy") rather than the more lenient rule ("leveling up"). (And here's Asher Steinberg with thoughts on implications for the travel ban.) I have given some thought to the leveling down/leveling up problem, and once tried to write an article about it, but I ended up shelving it in part because the problem was too hard.

For now, though, I have a more basic question about the judgment in the case. Justice Ruth Bader Ginsburg's opinion ends, "The judgment of the Court of Appeals for the Second Circuit is affirmed in part and reversed in part, and the case is remanded for further proceedings consistent with this opinion." The 2nd Circuit, for its part, had concluded that "Morales-Santana is a citizen as of his birth," and reversed and remanded the Bureau of Immigration Appeals. But what part of the 2nd Circuit's judgment, exactly, did the Supreme Court actually affirm?

Normally the Supreme Court affirms in part and reverses in part when the lower court's judgment extended to two separate claims, and got one of them right. Here, so far as I can tell, there is only one bottom-line claim—whether Morales-Santana is a citizen or not—though there are two different legal questions on the way to answering it.

To be sure, the Supreme Court agreed with part of the 2nd Circuit's opinion (the part holding the statute unconstitutional) but it seems to disagree entirely with its judgment. The 2nd Circuit reversed the BIA. The Supreme Court held that the 2nd Circuit should have affirmed the BIA on alternate grounds. (And as the Supreme Court sometimes says, it reviews "judgments, not opinions.") So shouldn't the Supreme Court have just reversed the 2nd Circuit, and if not, what part of its judgment (as opposed to its opinion) did the court affirm?

One possibility is Mark Tushnet's suggestion that the court is actually requiring the executive branch to exercise prosecutorial discretion in favor of Morales-Santana if possible, but nobody else seems to share that reading of the opinion and I don't think I do either.

Another possibility is that the court thinks that "holding a statute unconstitutional" is somehow a separate part of the judgment, something that can be affirmed separate and apart from any actual constitutional claim or remedy that is sought in the case. I don't think that's how federal courts work, but it is a conception of judicial power I see floating around sometimes.

A third possibility is that the opinion was forged in compromise, and it was important to some members of the court to get "affirmed" somewhere into the judgment line, even if it wasn't clear why.

The fourth, and most likely, possibility is that I am missing something.