What is a state of "rebellion" classified as?

Hi,

I have always been interested in the idea of tacit consent. I read in a Wiki article that, I quote: "The theory of tacit consent of the governed holds that if the people live in a country that is not undergoing a rebellion, they have consented to the rule of that country's government.[3]"
http://en.wikipedia.org/wiki/Consent_of_the_governed

So what is a situation in the United States that would be legally classified as a state of rebellion? It sounds kind of silly, as you would think it would be obvious. However, if one man, born in the US, vehemently opposes the current government but is kept under control by that government, does that still classify as a rebellion? If not, does that mean that his efforts aren't worth recognition enough to classify it as a serious issue? If so, then it sounds like there is no moral or ethical relevance in this decision; allowing a government that would strong arm people enough to keep them subdued.

So the question is: What conditions , legally, are required for the Country to be classified as undergoing a state of rebellion?

Thanks.