Today the Supreme Court affirmed the decision of the U.S. Court of Appeals for the Ninth Circuit in Flores-Villar v.United States, 4-4. (Justice Kagan did not participate.) The case raised the question whether the Court’s decision in Nguyen v. INS allowed for gender-differentiated citizenship rules that are not grounded in biolgocial differences between men and women, or whether such a distinction constitutes unconstitutional gender-based discrimination. Given the subject matter, there was reason to expect the Court would divide along traditional ideological lines. given that Justice Kagan did not participate, and the remaining eight justices divided evenly, one suspects that Justice Kennedy (coincidentally the author of Nguyen) joined the remaining liberal justices to vote for reversal.