Granted, the Supreme Court would likely agree with that assessment. The Court has basically stretched the commerce clause to the point that it allows the federal government to do anything it wants. But you should keep in mind, if the Court were to issue an opinion asserting unicorns exist, that would not mystically conger them up out of thin air.
In fact, the federal government possesses zero authority to regulate firearms.
Even without the Second Amendment, the feds would enjoy very little firearms regulating authority. The Constitution does not delegate any firearm regulating power to the federal government, so that authority remains with the states and the people.
But the people of the states insisted that “further declaratory and restrictive clauses should be added” to “prevent misconstruction or abuse of its powers.” The Bill of Rights, including the Second Amendment, further restrict federal power.
“…the right of the people to keep and bear arms shall not be infringed.”
Infringe: to reduce or impair in any way.
Even while exercising legitimate constitutional powers, the federal government may not reduce or impair the right of the people to keep and bear arms in any way. So, although the feds have the power to regulate interstate commerce, they do not have the power to infringe on the right to keep and bear arms in the process.