And the need for it (at least on consitutional matters) has been largely obviated by the fact that we have a concise written Constitution, which anybody can refer to. Since past judicial decisions are, as Scalia says, evidence of the law, and are not the actual law itself, they're useful in determining unwritten common law. But they're not needed in determining the written Constitution that's sitting right in front of us, and was designed for the people to be able to understand.
Exactly. As he points out, you don't need to know what the individual founders MEANT by the words of the Constitution, either, which is how "wall of separation" got dragged into the discussion. You only need to know what the words, phrases, and general ideas meant to an ordinary, educated person at that time.
So it does help to have some acquaintance with Common Law, Natural Law theory, John Locke, the Bible and the Ten Commandments, and a few other background matters that the Founders drew on and took for granted as part of their mental equipment. But you still go primarily by the words themselves.
This is a fun essay and worthwhile to read for understanding ... yet Scalia fails at Schiavo. The Court, even bound by strict originalist Constructionism could have rescued her. No law set by man is greater than the basics of the Creator's Natural Law -- no State can legalize murder.