The Interstate Commerce Clause is in Article I, Section 8, Clause 3, and it's an affirmative grant of power to regulate commerce among the states. And that Commerce Clause was adopted because of the historical background, where you had states that were engaging in trade disputes with each other that were erecting trade barriers between each other. And in some cases we're even engaging in battles over relative trade disputes. And so the Framers put in and then the ratifiers or adopted the Commerce Clause to make interstate commerce a national issue. To give the federal government the national power to ascertain how interstate commerce is going to occur, to make it more efficient, and then in particular to protect interstate peace. But what happens when Congress doesn't act? What happens when Congress doesn't pass a statute and a state erects a trade barrier against another state's importation or exportation of goods and services. Does the Commerce Clause have anything to say about that? The Supreme court from some of its earliest opinions, the earliest one being Gibbons versus Ogden under the Marshall court identified a dormant, or implicit, or silent aspect to the Commerce Clause. So that way, when even Congress, when Congress doesn't act, the Commerce Clause of its own authority continues to limit the ability of states to impede trade across its borders from its sister states. The Dormant Commerce Clause is a longstanding part of our constitutional jurisprudence. It is criticized. There are two branches of the Dormant Commerce Clause, one branch of the Dormant Commerce Clause identifies what are called intentional discriminations against out-of-state commerce. And then there's another branch that identifies and regulates unintentional restrictions by a state of out-of-state commerce. And the Dormant Commerce Clause doctrine currently limits both of those, although it limits them differently. And what the critics argue for the most part in Justice Scalia of recent memory and Justice Thomas have made this argument that they believe that the non-discriminatory part of the Dormant Commerce Clause doctrine is not justified by the original meaning of the Dormant Commerce Clause, but that the intentionally discriminatory aspect of the Dormant Commerce Clause doctrine is in fact justified by the original meaning, or they're a little bit cagey about this, or at least it's close enough. And there's a lot of precedent on a point, so they're not going to overrule it. So the Dormant Commerce Clause is the restrictions that the Commerce Clause itself imposes on states even when Congress doesn't act. The American constitution has many ways to protect federalism. And many of those protections of federalism have, especially since the New Deal, become less important, but the Dormant Commerce Clause is not one of them. It continues to be a very important tool for litigants to use, to challenge state economic regulations. And, I'll give you an example: Michigan, which is a state near where I live, has been for years trying to cultivate a domestic wine industry. And one of the ways that Michigan did, it did so in a variety of ways, but one of the ways was: it put a tax on out-of-state wine that Michigan did not impose on in-state grown wine. And, primarily the tax hurt wine that came in from California. And so Michigan's differential treatment was challenged in the Supreme Court and the Supreme Court had no problem striking down that Michigan differentiation because Michigan had intentionally adopted that differentiation because it wanted to prioritize and build up its own domestic wine industry. So students look at the Dormant Commerce Clause, and they think, oh boy, it's just more Commerce Clause, but actually it's a strong tool. It's a strong body of doctrine that many litigants continue to use today to challenge state economic regulations, which under our current constitutional dispensation is actually a relatively rare post New Deal.