A trademark owner can enforce its rights using both state unfair-competition law and the federal Lanham Act. Because a Lanham Act infringement claim is a cause of action arising under federal law, it can be, but doesn’t have to be, brought in federal district court. In other words, federal courts have jurisdiction over Lanham Act claims, but their jurisdiction isn’t exclusive. A trademark owner can bring its federal infringement claim and any related state-law claims in either federal or...