The most important recent development in originalism has been the recognition that the Constitution was not created ex nihilo but against a pervasive legal background. As result, its interpretative context is profoundly infused by law. This recognition has led to at least four different ways in which originalism has been thickened.
First, whole clauses in the Constitution are not comprehensible without understanding a complex body of preexisting domestic law, including rules of interpretation, of which most modern readers would be oblivious. A fine example of the importance of this approach is the article Preemption by Caleb Nelson. Here Nelson shows that the phrase “anything in the law notwithstanding” which appears at the end of the Supremacy Clause in Article VI, is not just verbal filler but a familiar kind of legal signal called “non-obstante” clause. It was added to the Constitution to block a rule of interpretation that required courts to harmonize prior statutes with subsequent statutes even if on their face there was an appearance in conflict. This discovery has real bite: it indicates that there is no general presumption against preemption.
Second, it is not only domestic rules that form the background for fixing constitutional meaning. In The Law of Nations as Constitutional Law, Anthony Bellia and Brad Clark suggest that provisions, like the President’s power to send and receive ambassadors, and the Congress’s authority to declare war, can be understood only by reference to background principles of the law of nations. This article too has much contemporary relevance since it justifies application of the settled principles of the law of nations to override state law to protect such Article I and Article II powers of the federal government.
Two other examples of thickening originalism may even have more far reaching consequences because they are not focused on specific clauses, but are of general application.