The main issue in the Supreme Court case of California v. Federal Power Commission was whether the Federal Power Commission (FPC) had the authority to regulate the sale of electricity between two utilities that crossed state lines, in this case, Southern California Edison and Colton, California. The FPC had asserted jurisdiction over the sale under 201b of the Federal Power Act, which extends federal regulatory power to the sale of electric energy that crosses state lines. However, California had argued that the FPC did not have jurisdiction, as it had been regulating the sale for some time under the California Public Utilities Commission. The Supreme Court ultimately sided with the FPC, stating that the Federal Power Act did give the FPC the authority to regulate the sale of electric energy that crossed state lines. This case was significant as it established the FPC's authority to regulate the interstate sale of electricity. It also highlighted the complexities of jurisdictional issues between state and federal regulatory bodies.