The case lays out the current understanding of Congress's power over commerce:

"Consistent with this structure, we have identified three broad categories of activity that Congress may regulate under its commerce power... First, Congress may regulate the use of the channels of interstate commerce... Second, Congress is empowered to regulate and protect the instrumentalities of interstate commerce, or persons or things in interstate commerce, even though the threat may come only from intrastate activities... Finally, Congress' commerce authority includes the power to regulate those activities having a substantial relation to interstate commerce, i.e., those activities that substantially affect interstate commerce."

Thanks for clarifying, that does seem to imply pretty widespread authority. What if commerce is only an incidental use of something, though? Commerce is related somehow to a huge number of things which couldn't be considered primarily commercial. There has to be some reasonable limit placed on these things. The internet, radio, newspapers, and so on are not used primarily for commerce.