In the case of Katzenbach v. McClung (379 U.S. 294 (1964)), a restaurant just off an interstate highway was accused of racial discrimination, (a violation of the 1964 Civil Rights Act). The restaurant argued that the law shouldn't apply to them because they weren't engaged in interstate commerce and were therefore beyond the reach of the Interstate Commerce Clause. However, in a decision similar to Heart of Atlanta Motel v. United States (379 U.S. 241 (1964)), the US Supreme Court found that racial discrimination had a "restrictive effect upon the interstate travel of Negroes." Therefore the law was within Congress' authority under the Interstate Commerce Clause. In addition, the Court felt that the fact that the restaurant bought food that was bought from a guy who got it from out of State gave them enough of a hook to give jurisdiction. In this case, most of the sales were to locals. So can you say that the purchase of ingredients from out of State makes this restaurant an agent of interstate commerce? That's really pushing it. This decision was a repudiation of the theory of A.L.A. Schechter Poultry Corp. v United States (295 U.S. 495 (1935)), which said that interstate commerce stops at the processing plant. In a concurring opinion, The Act was justified based on the aggregate theory of commerce first talked about in Wickard v. Filburn (317 U.S. 111 (1942)). The Court stated that if Congress felt it needed to pass the 1964 Civil Rights Act as a part of the Interstate Commerce Clause, then the Court should be maximally deferential to Congress, since they are the ones who are supposed to determine what the limits of the Interstate Commerce Clause is. Under the 14th Amendment, it is still unclear that Congress can go after individual acts of discrimination. The language of the 14th Amendment is "No State shall...", so the Federal government can go after actions by the States (such as segregated schools), but it is ambiguous as to whether they can go after private, non-State actors (such as in this case). That's why the Courts have used the Interstate Commerce Clause instead of the 14th Amendment to go after cases of private discrimination. By comparison, the 13th Amendment explicitly prohibits individuals from owning slaves.