The Supreme Court invented the concept that arms must have a connection with a well-regulated Militia in order to be protected by the Second Amendment. The Second Amendment, however, creates no such requirement. Our Founders recognized that "arms" are anything that can defeat tyranny and ensure liberty. A handgun without a serial number is not only just as effective when fired as those with a serial number, it has the added benefit that it is almost impossible for a tyrannical government to trace it or prohibit its possession through prior restraint.
The federal requirement for serial numbers is the most serious infringement of all as it is an enabler of almost all the other infringements.
What would we think of the protections of the First Amendment if the federal government required serial numbers on every issue of every newspaper or if every book published had to be registered?