So the Commerce Clause has been litigated in the Supreme Court probably more often than any other structural provision of the Constitution. And the most important early case was called Gibbons against Ogden and it involved a state law that granted a monopoly to people operating a steamship across the Hudson River between New York and New Jersey. And the Supreme Court held that a federal law, which licensed a competitor, trumped the state law and thus the national government's ability to be able to promote commerce or protect commerce against local monopoly legislation was upheld. This can be seen as a very nationalistic decision in a sense, but I think it's exactly what the Commerce Clause was intended for. It was giving the national government the ability to protect a national market against the neo-mercantilist policies of individual states. In the decades after Gibbon, the Supreme Court tended to distinguish between commerce, which it understood to be the transportation and sale of goods, versus the production of goods, so agriculture and manufacturing were not considered to be directly regulable by a national government, but trade was. As the national economy grew more integrated, the Congress began passing major economic legislation, like the antitrust acts, which regulated not just commerce, but also manufacturing. And in several cases around the time of the New Deal, the court came to the conclusion that all economic activity, including manufacturing and agriculture, which was destined for a national market, was directly comprehended within the Commerce Clause and so you had cases like United States versus Darby: there could be national labor regulation in manufacturing. The farthest and most extreme case of the period, Wickard versus Filburn, regulated agriculture all the way down to the production of wheat by a farmer for consumption by his family and by his own animals. And that's where things rested for many decades after that and almost anything Congress did to regulate economic activity was going to be upheld. And then in more recent times, as Congress has passed laws regulating activities that aren't even economic – there were two cases called Lopez and Morrison – the court has begun to draw lines and and actually strike down some acts of Congress uh on the ground that what was being regulated was neither economic, nor interstate. And then the final example of this, and probably the most controversial ah was the Supreme Court's consideration of the Affordable Care Act, or Obamacare, and its requirement that everyone purchase approved health insurance policies. And the Supreme Court, in a very contentious five to four majority, held that the Commerce Clause does not empower the government to do that, that when individuals choose not to purchase a product, that they are not engaged in commerce and since they're not engaged in commerce, they're not doing something Congress can regulate. In effect, Congress can regulate commerce that takes place, but it can't force people into commerce. And so the court did, in fact, uphold the individual mandate, but not under the Commerce Clause.