Here is an example:
The concept of "authority" is a moral concept. "Government," by definition, is the group of people who have the supposed moral right to enact and enforce "laws." (Whether there are "limits" on what those "laws" require doesn't matter for this particular point.) And a moral right of the "law-makers" to rule (even if only in a "limited" way) implies a moral obligation to obey on the part of their subjects. That is the essence of the concept of "authority" and "government."
Now here is one painfully simple proof of why that concept is self-contradictory bunk:
From the perspective of any given subject, each "law" either coincides with his own conscience, or conflicts with it. For example, a "law" may declare that murder is "illegal," and an individual may think that murder is inherently immoral anyway--so the two match. On the other hand, a "law" may require an individual to fund a war that the subject believes to be immoral, in which case there is a conflict between his own conscience and "the law."
Okay, here comes the question. (Statists, brace yourself, because this might be both painfully obvious and existentially disturbing.) Ready?
Question: Can an individual ever have a moral obligation to disregard his own moral conscience, in favor of obeying an "authority" instead?
Here are the two possible answers, along with their logical ramifications:
1) YES, a person CAN have an obligation to go against his own moral conscience. In other words, a person can have a moral obligation to do something which he believes to be immoral. I hope I don't need to explain in too much detail why that answer is insane. In short, it can't be good to be bad; it can't be moral to be immoral; committing evil cannot be virtuous. Even if a person's own judgment is flawed and twisted, he still cannot rationally imagine himself to have an obligation to do what, from his perspective, is the wrong thing to do.
Okay, so that answer stinks. Here's the other possibility:
2) NO, a person CANNOT have an obligation to go against his own moral conscience. Therefore, he has no obligation to comply with any "law" that conflicts with his own personal judgment of what is right.
Most people can handle that much (even if they start getting nervous at this point). But here is what directly and logically follows from that:
If a "law" conflicts with one's conscience, he has no obligation to obey it. Such a "law" should have no "authority" in his eyes. If, on the other hand, the "law" coincides with his one's conscience, such a "law" is, at best, unnecessary. It is his own conscience, not any "legislation," which obligates him to act properly. Which means that such a "law" still should have no "authority" in his eyes.
In other words, in no situation should any "law" have any "authority" in anyone's eyes, whether it coincides with or conflicts with one's own moral conscience. Every "law" either matches one's own judgment, and is therefore unnecessary and irrelevant, or it contradicts one's own judgment, and should be ignored. Which means that no man-made "law" ever has any "authority" (i.e., it never carries an inherent obligation to obey). And without any "authority" to its "laws," "government" loses all legitimacy, ceases to be "government," and becomes nothing but a bunch of bossy control-freaks and their mercenary thugs.
So those are your choices: "anarchy," or being morally obligated to be immoral. I would be happy to see any attempt by a statist to offer some other rational answer to the question, but I won't hold my breath.
"Must the citizen ever for a moment, or in the least degree, resign his conscience to the legislator? Why has every man a conscience then? I think that we should be men first, and subjects afterward. It is not desirable to cultivate a respect for the law, so much as for the right. The only obligation which I have a right to assume is to do at any time what I think right." - Henry David Thoreau