Solicitor General Elena Kagan will be President Obama’s second Supreme Court nominee. The emerging conventional wisdom is that Kagan, a rare nominee for the high court who hasn’t been a judge, is a very smart blank slate. On at least one category of issues that Kagan will face — the intersection of national security and law during a time of war — that conventional wisdom looks correct. But there’s a proxy for that set of issues, however inexact, that offers a few clues in advance of her confirmation hearings: Kagan’s deference to executive power.