If it comes to that, whether there's a legal right to have said guns is pretty much moot, because the people you're using those guns to resist aren't going to respect that right. If you're prepared to fight your government, you don't care whether it's allowing you to have the means to fight it.
Therefore the right to bear arms as a defense against tyranny is mostly empty words. The way to prevent tyranny is robust public institutions and a democratic culture. Weakly democratic states fall to autocrats all the time. There is no culture of democracy so the number of power holders a would-be autocrat has to cow is few. Democracy, real democracy, involves orders of magnitude more people, it's that much more difficult to overthrow.
Easier to already have a gun from when they were allowed, then to acquire a gun after they were banned.
Of course the later would never be hard in America, considering just how many guns there are that would not get swept up... But the first is still easier.
Therefore the right to bear arms as a defense against tyranny is mostly empty words. The way to prevent tyranny is robust public institutions and a democratic culture. Weakly democratic states fall to autocrats all the time. There is no culture of democracy so the number of power holders a would-be autocrat has to cow is few. Democracy, real democracy, involves orders of magnitude more people, it's that much more difficult to overthrow.