The burden of proof - in the case of action against another person - would certainly lie with the one claiming the right to act. If an individual is minding his or her own business, harming nobody and not depriving anyone of their property, and another person comes along demanding action from them, taking action against them, or attempting to take their property, then surely they must provide the justification for it. A simple thought exercise would go like this:
Person 1: "Give me your spear."
Person 2: "Why?"
Person 1: "Because you need to give it to me."
Person 2: "Why?"
If ownership of the spear is established, then the reason why Person 1 wants or needs Person 2's spear would need to be explained if the object is to persuade Person 2 into giving up the spear. The same applies in this scenario:
Person 1: "Give me your spear or I will hurt you and take it."
Person 2: "Why do you have a right to hurt me and take my spear if I don't want you to have it?"
The burden of proof hasn't changed. Person 2 doesn't need to explain why Person 1 should not hurt him and take what does not belong to Person 1.
For a statist to argue that the state has a right to make demands, to force people to act, and to prevent people from acting, they must provide the proof for how the state actually acquired this power. The burden has always been on them and yet, they have so far been unable to provide any proof other than some sort of special pleading fallacy, usually in the form of an implied/coerced "contract" that would otherwise be laughed at in the real world in personal and business relationships.
If it's not special pleading then it's argumentum ad baculum; you're absolutely right. How could there be a contract if there's no capacity to not agree to the contract without it resulting in violence being used against you? Would they say that there's a contract between a mugger and his victim? How about between a rapist and his victim? Doubtfully. Excellent points man
Any type of system that a statist advocates that involves some form of "democracy" or "representation" rather than outright violence (might makes right), is a system that at some point must have been voted on unanimously by its members. In order to have a democratic election, you must first have agreement on the democratic process itself. The regression never holds to any actual unanimous consensual agreements.
So, basically, there is no proof of any consent to be governed if you as an individual have not consented to it. There's simply no getting around that fact...except to effectively say, "Comply or die," or "Love it or leave it" if you're allowing them to escape. Both are equally morally repugnant and logically inept arguments.