The people who believe so rests their arguments on two things:
1. The commerce clause that grants the federal government the power to regulate commerce between the states.
2. The federal ability to levy exise taxes. The ATF was originally under the Treasury to collect taxes on firearms.
The massacre of men, women, and children at the Branch Davidian compound in Waco during the Clinton administration was instigated by the ATF on the grounds that Koresh did not pay taxes on guns he purchased.
This was the same charge that led the FBI to attack the Randy Weaver family home at Ruby Ridge, ending with the agents killing Mrs. Weaver, who was holding her baby, their twelve year old son, and the family dog. Democrats think we have forgotten their shameful crimes against American citizens, but some of us remember.
the commerce clause - so abused
When talking about the commerce clause, it is very important that the word States is capitalized. The commerce clause was never intended to regulate commerce between The People. The People are not even mentioned in it! When it was written into the Constitution, we had The People, the States, and the Feds. It was written to prevent a State from enacting tariffs on another States goods and services. It was not meant to regulate commerce between The People. It has been purposely mis-read by the black robed terrorists to give the Feds power over everything.