It has been argued that the point of the 2nd amendment is to overthrow a tyrannical government.
In the Declaration it states that “whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government.”
At what point "Legally", are we allowed to overthrow the government?
Think through the logical combinations of two questions: The government is tyrannical or just, the revolution is successful or not.
So 'legal' is the wrong category for your question. The 2nd Amendment allows the citizens to stockpile arms, which helps both justified and not justified revolutions. Finding the justification for a revolution is a moral category, not strictly a legal question.
At what point "Legally", are we allowed to overthrow the government?
Never.
But, if you are successful, the government you have overthrown can't prosecute you for it, since it no longer exists.
It is pretty much never legal to engage in a revolution against the currently established government. Not by the laws created by and supporting that government, it isn't. I am reminded of the couplet by John Harrington:
Treason nae'r doth prosper, what's the reason?
Why if it prosper, none dare CALL it treason.
The US Declaration of Independence was a political document, attempting to justify a revolution then in progress, it was not and is not a legal document, and it does not make actions similar to those undertaken by the Americans who revolted against Britain legal in future.
A revolution may be justified. It may even be morally essential. But those are judgement calls. No court, except the court of public opinion, and later the court of history, will rule on them.
There is no mechanism in existing law that states that allows for some kinds of revolution to be legal.
The Second Amendment as currently interpreted allows people to purchase and posses firearms and other weapons, and rules out most regulations of such ownership, although not all. The formal reason for this in the amendment itself is:
A well regulated Militia, being necessary to the security of a free State ...
That would suggest a possible need to call on the militia to defend the country against foreign invaders, or possibly against revolts. Nothing in it says that the purpose is to allow the people to oppose tyrannical governments. At the time the US Constitution was written, the militia was considered to be an important source of reserve military power against invasions and rebellions.
The relatively recent US Supreme Court decisions which used the 2nd amendment to overturn local gun control laws cited the need for an ordinary, law-abiding citizen to be able to defend against criminals, particularly against home invasions. That case was in the context of a law which made it almost impossible for anyone to lawfully own a handgun, even an off-duty police officer. It explicitly said that some regulation would be permitted. It did not in any way say that ownership of weapons would be useful for legal rebellion, or justified rebellion.
As the answer by o.m. says:
The 2nd Amendment allows the citizens to stockpile arms, which helps both justified and not justified revolutions. Finding the justification for a revolution is a moral category, not strictly a legal question.
I fully agree.
The answer to this question depends on one's perspective about what the law is.
Through the positivist lens, a revolution against a government (assuming such government has at least formally enacted rules against such acts) will always be illegal. For example, Bentham and Austin both asserted that "it could not follow from the mere fact that a rule violated standards of morality that it was not a rule of law" (HLA Hart, "Separation of Law and Morals", Harvard Law Review (1958), p. 599). However, Hart would also argue that just because something is a law need not entail it is to be obeyed (ibid, p. 618).
Natural law theorists (e.g. Lon Fuller) would require that for something to count as a law, it must adhere to basic principles of legality, some of which would include basic principles of morality. One could say, "This thing is the product of a system so oblivious to the morality of law that is not entitled to be called a law." (Lon L. Fuller, "Positivism and Fidelity to Law: A Reply to Professor Hart", Harvard Law Review (1958), p. 661).
It is never legitimate to overthrow a legitimate government, except via means prescribed thereby (e.g. elections), but not all groups of people claiming to have legitimate authortity, actually do.
One could view a document like the Constitution as a sort of "instruction manual" for the government, which citizens should use in case of uprising to determine when they should support the legitimate government in putting down unlawful rebellious actions, and when they should protect fellow citizens against lawless actions by rogue government personnel.
Since it has not been touched on with other answers. Law and legal is based on the premise of a sovereign and the sovereign having a monopoly on violence. In a successful revolution, a new sovereign is created and hence the previous monopoly has ended. The new sovereign now decides law and legality, if it has the power to do so.
Revolution usually also suggests that the sovereign has lost lawgiver status due to acting contrary to natural law.
Another point in revolutions, not all have to be full out jacobinistic. e.g. All previous key holders (holders of powers) need not be killed. e.g. Bloodless coup.
Most governments see themselves as good governments. And they might have laws that make it legal, perhaps even required, to overthrow a bad government. Of course it's not legal to overthrow the current government, since they are good.
Now a bad government comes into power. Of course they don't want to withdraw that law and basically proclaim that they are a bad government that way. So the law remains. Since they are a bad government, overthrowing the government is legal, perhaps even required.
Of course if you want to make use of that particular legal right, you risk being shot or worse.
