A few years ago, (1942, to be exact) the Court held (in Wickard v. Filburn) that Congress could apply national quotas to wheat grown on one's own land, for one's own consumption because it could affect interstate commerce, thereby eliminating any barrier to Congress passing any law it wanted under the Commerce Clause. The federal government was officially all-powerful.
regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes;
There is a new challenge to the Commerce Clause and it is currently in the Ninth Circuit. Montana passed a law that allows firearms manufacturers in Montana to ignore federal law if their product will only be sold within the state. Their claim is that without actual interstate commerce the federal government has no authority to interfere with the citizens of Montana who comply with Montana law. Apparently quite a few other states have passed similar laws. This case has implications beyond the Second Amendment and the issue of firearms. For example, marijuana legalization proponents have made similar arguments.
It has often been pointed out that those on the left and right of the political spectrum often have coinciding interests but fight each other out of sheer stubbornness. It will be interesting to see whether the left will join the gun rights community to argue against the federal government and to see how the Supreme Court justices will split if this case comes before them.
The Cato Institute has filed an amicus brief with the Ninth Circuit and has an update about their testimony here.