Never, if we accept the intent of the 2nd amendment is to stop a tyrannical us government it does so be making sure you have the means for a rebellion (or the states actually). In that case you would not be judged for your actions like a criminal.
It of course does not apply to individuals taking action on their own (and they alone would not be able to bring down a regime). The best you could hope is a pardon/amnesty by a new pro democracy president/authority, if you are still alive.