QUESTION: I was wondering if the "jurisdictional element" relates to the rules of personal jurisdiction, or if it is much broader and refers to any attempt to define or limit the particular legislation with respect to interstate commerce?
ANSWER: It is wholly unrelated to the idea of personal jurisdiction. Rather, as I think your second clause indicates, it concerns Congress's legislative jurisdiction. A jurisdictional element, as meant in Lopez, is nothing more than additional language that ensures that the particular instance of the activity being regulated has some sort of a connection to interstate commerce. For example:
* law without a jurisdictional element: "It is unlawful to possess a gun in a school zone."
* law with a jurisdictional element: "It is unlawful to possess a gun that has traveled in interstate commerce in a school zone."
The emphasized clause is a jurisdictional element. And it is so called because its purpose is to bring the statute within Congress's commerce power -- that is, its legislative jurisdiction.