The U.S. Congress possesses no legislative power that cannot be traced to the U.S. Constitution. Article I, §8, Clause 3 of the U.S. Constitution provides that: This is known as the Commerce Clause. There are three categories of activities subject to congressional regulation under the Commerce Clause. Congress may regulate the use of the channels of interstate commerce, or persons or things in interstate commerce, although a threat may come only from intrastate activities. Finally, Congress may regulate those activities having a substantial relation to interstate commerce (i.e., those activities that substantially affect interstate commerce).