A. John Simmons considers an objection from Hanna Pitkin that "terms like 'authority,' 'law,' and 'government' are grammatically or conceptually tied to 'obligation,' in the same way that 'promise' is." As Pitkin writes, "it is part of the concept, the meaning of 'authority,' that those subject to it are required to obey, that it has a right to command." (39)
This is a confused mess. At the very most, the term "government" ceases to have a reference, when most people actually refuse to obey. In such a case, a government may indeed fall. Even that is not 100% certain, since such an unpopular government may be able to endure in the very short term through an attempt at repression.
There is no way to get from that to the idea that I personally right now have a duty to obey (which government?); nor that the term "government" ceases to have a meaning if I or whoever else decides to disobey some or another government.
The fact that today I may have exceeded the posted speed limit once or twice does not entail that I and Pitkin can suddenly not discuss problems of political philosophy without hopelessly equivocating on the word "government."