At National Review's The Corner, Andy McCarthy expresses confusion --
What Is "Settled" Law?
Judge Sotomayor answering Sen. Hatch [almost a quote]: All decisions of the Supreme Court I consider 'settled law' to the extent that the doctrine of stare decisis (respect for precedent) applies.
In other words, all law is settled ... except when it isn't.
Well Yes. He might want to direct his question to the Chief Justice of the Supreme Court --
SEN. SPECTER [as read into the record by Sen. Feinstein]: "Judge Roberts, in your confirmation hearing for the circuit court you testified: 'Roe is the settled law of the land.' Do you mean settled for you, settled only for your capacity as a circuit judge, or settled beyond that?"
ROBERTS: "Well, beyond that. It's settled as a precedent of the court, entitled to respect under principles of stare decisis. And those principles, applied in the Casey case, explain when cases should be revisited and when they should not. And it is settled as a precedent of the court, yes."
SPECTER: "You went on to say then, 'It's a little more than settled. It was reaffirmed in the face of a challenge that it should be overruled in the Casey decision, so it has added precedental value.'"
ROBERTS: "I think the initial question for the judge confronting an issue in this area, you don't go straight to the Roe decision. You begin with Casey, which modified the Roe framework and reaffirmed its central holding."
Thus "settled law" is indeed a precedent that stands until it doesn't, which is the wheeze that John Roberts came up with to get through his confirmation hearing. Looks like Sonia decided to follow precedent!