I'm sorry I dont understand your first statement. If Robin Hood was not a citizen of a representative republic, then he had no chance to agree or disagree with any law passed, so the "social contract" you cite did not exist for him. Conversely, if the tea party are members of a representative republic, then the social DOES apply. They have to obey the laws, even if they don't like them, because the way the representative republic works is that the majority opinion is always the way forward, and they were outvoted in the last election. Tough luck for them.
The eighth commandment does not have any qualifications. But its not the only commandment. By your argument, for fear of breaking God's eight commandment, people have no recourse against others cheating them, ripping them off, oppressing and murdering them.
Robin Hood may have been absolved of his duties under social contract, since (ostensibly) one did not exist. But as I said, the offense he committed was not against King John, but against God.
Stealing from those who stole from you -- or, in the case of Robin Hood, others he claimed to "champion," -- is still theft. There is recourse against those offenses, certainly, but not by answering theft with theft.
I say that fully knowing that this is not a perfect world, and admitting that I would be one of the first to take up arms against those who would rob me.