That's part of what Rule by Men means... Men can overthrow each other. That's what the Nobility have done since the social contract was established in the 6th and 7th centuries...
Theoretically, no government can continue unless it has the tacit acceptance by it's governed. It maters little whether by force, coersion, popularity, social morality, or religious authority. If people stop accepting that a government has rightful authority, they then begin to undermine it. (Several great minds make this point in other wordings, including Marx, Franklin, Hitler, Lenin, and even to some extent Mahan and several Popes.)
Rule by Men rather than laws also means that it's a fair site on the dangerous side to go beyond custom. (Men are inherently ruled by custom... hence why in Alaska, Marijuana is still common and seldom prosecuted save for major grow ops, despite possession being a federal crime....)
I could, for example, go to my neighbor, and buy some pot. Definitely unlawful. Socially acceptable. Likewise, a cop could ask me to do so while wearing a wire, in order to bust my neighbor. Lawful, yes. But beyond custom. His Lt would chew him for wasting time on a minor pot bust, the news would release his name, and thus he'd be ridiculed, and the judge would probably throw it out, too, for invasion of privacy. All because of customs in violation of law.
Now, when law goes away, we still have custom.
They can just fine get away with breaking laws, since those are local things, provided they can justify them for the good of the imperium. But those other men in power better agree, or "Off with his head" would be a release....