The answer to this question is important for determining if there are any limits to the authority of government and, if so, what those limits are. It will help us to understand when those who wield the power of government have gone too far in the exercise of that power. It will help us to identify when groups of people actively seek to manipulate government to do things that are an abuse of its power.
One position is that, by establishing a government over themselves, the people automatically yield or even negate what authority they possessed for themselves. The government now rules supreme by virtue of its existence and essentially gets to decide what powers it has. This view also empowers the government to determine what rights belong to the people. It can grant (or revoke) rights with impunity without regard to what the people believe or want.
Another position is that all government authority originates from the people. Because government only truly exists by the consent of the governed, they are the source of its authority and actually determine what powers of authority the government possesses. This means that the people can grant or revoke any power of government. They could conceivably revoke authority to the point where government cannot effectively do anything it actually should do. Another implication of this is that the people could actually grant the government so much authority that it effectively becomes the type I described above.
A third position is a kind of variation of both of these. A government only truly exists if it is accepted by the people. This acceptance doesn't have to be universal. If the people, through active participation, complacent acceptance, or some degree of fear abide by a government's decrees, then they have accepted the government. Once a government exists, it continues to rule until it either collapses or is successfully overthrown. This is important to realize in the case of revolutions. Revolutionaries are called “unruly” because they refuse to be ruled by the established government. Does this lack of consent mean that the government ceases to exist? No. If there is no established government, there can be no revolt against it. Therefore, even the revolutionaries give some form of acknowledgement to its existence. This, however, doesn't address what powers the government has.
This third position holds that government has certain powers by its existence, but those powers are defined by human nature and the needs of the common good of people living in community. The distinction between this and the first position is that this authority is not actually yielded by the people and the government has no true authority to determine what rights belong to the people. The distinction between this and the second position is that the people cannot legitimately grant powers to the government that interfere with the rights of the people, nor can they legitimately revoke powers that properly belong to the government. This is the case regardless of the form of government and the method of establishing particular laws. This even applies to multiple levels of government, where the different levels cannot legitimately interfere with the proper functions of the other levels. In determining exactly what those powers are, this position relies on the common good of people living in community, which can only be properly understood if we have an adequate understanding of human nature.