You may not believe that anyone can prevent you from protecting yourself against tyranny, but reality suggests otherwise. I do not know where you live, but I am relatively certain that wherever it is, there are laws, and men in blue uniforms to enforce those laws, that prevent you from adequately defending yourself from tyranny. You claim they don't have this authority to deny you the things you require; they, however, would disagree.
People get authority from wherever they please. The criminal gives himself authority to do as he pleases, whether you recognize his authority or not.
You might argue that the criminal does not have the authority (or the right) to rob you; he, however, would disagree.
The point I was making was that the Constitutionality of gun ownership is an irrelevant argument since militias, as specified in the Constitution, do not exist anymore. And since militias don't exist anymore, the Constitutionality of owning a gun is no longer a "protected right."
But like you....this is just my opinion.
RE: The Second Amendment, another look.