"[N]ot every closely divided opinion splits the Supreme Court along ideological lines."

Says Jonathan Adler:

In Carr v. United States, the Supreme Court held, 6–3, that the Sex Offender Registration and Notification Act (SORNA), which requires convicted sex offenders to register with local authorities when they move from one state to another, does not apply to sex offenders whose interstate travel occurred before the Act went into effect. This holding enabled the Court to avoid consideration of whether SORNA’s registration requirement violates the ex post facto clause. Justice Sotomayor wrote the opinion for the Court, joined by the Chief Justice and Justices Stevens, Kennedy, and Breyer. Justice Scalia concurred in part and in the judgment. Justice Alito dissented, joined by Justices Thomas and Ginsburg.