In their first full term together on the Supreme Court, Chief Justice John Roberts and Justice Samuel Alito voted alike more than any other pair of Justices. According to U.S. Law Week, the pair disagreed in only 6% of the cases decided in the 2006 Term; by my count, the two reached different conclusions only five times. This overwhelming level of agreement between the two new Justices makes their disagreement in last term’s
federalism cases all the more striking....