Who cares?
There's a member of a well regulated state militia. That person is carrying a weapon. The federal government may not infringe that person's right to keep and bear that weapon.
The second amendment doesn't state that the weapon must belong to the person. The second amendment doesn't state who that person shall be or shall not be. The second amendment doesn't say what the arm shall or shall not be.
Militia member. Gun. Protected.
What right? How does this situation differ at all from an agent of the state carrying out the powers of the state under state control? Surely the Founding Fathers didn't think soldiers needed legal protection to carry weapons!