There is a good discussion of constitutional originalism over at The Volokh Conspiracy – sparked by a post by Randy Barnett:
Of course, like history, originalism can be practiced badly, by cherry-picking or distorting the evidence of meaning to reach a preordained conclusion, which is why I resist relying upon the findings of any particular originalist work that had not been critiqued or confirmed by others who know that particular subject, however excellent and sensible I may find it to be. And the original meaning of the Constitution may not always be sufficient to decide particular cases and controversies without the development of constitutional doctrine that is not itself in the Constitution, but is needed to implement what is. It was mistake of the old originalism to try to resolve all current cases by asking “how the Framers would have decided them.” That is really a counter-factual question, not an empirical one about meaning. Yet the doctrine that is necessary to implement what the Constitution says is also found in written legal texts expressed by language that lawyers are trained to understand without the assistance of historians.
If it was genuinely not possible to identify the meaning of language at a previous point in time, then old contracts could not be enforced according to their meaning at the time of their formation (which is what the law of contracts requires), old statutes would be a mystery and impossible to follow or enforce, and classic Supreme Court opinions would be impossible to understand. The only language that is claimed to be inscrutable mystery to lawyers (but not historians) is the foundational law provided by the U.S. Constitution. How are we lawyers able to follow the 200+ year-old-opinions in Marbury, Gibbons and McCulloch, but not the Constitution itself, written a mere 30-40 years earlier? Has anyone seriously suggested that lawyers need to consult historians to tell them the communicative content of these precedents?
The reason for claiming that the Constitution alone among legal texts is inaccessible to lawyers is not that its original communicative content is unclear, but that some of its original meaning is all too clear and some people don’t like it, so it must be gotten rid of somehow. The Progressives were very candid about this, referring to the “Horse-and-Buggy” Constitution. They knew what it meant, but it got in their way. So, for better or worse, the written opinions of long dead New Deal and Warren Court Justices have replaced important parts of the the written text of the Constitution. You don’t need to be a historian to know there’s a difference in meaning between the two sources of law, but it helps to be a lawyer.