Edwin Vieira in his article A PRIMER ON 'MARTIAL LAW', suggests one form of martial law is as follows:
When the county/comte electorate disappears due to fire, plague, or they all become swallowed up by a municipal corporation, does such effect the situation where "no effective civilian government exists"? I suggest: yes. That is why the law enforcement changes from exercise of the shrieval power to the exercise of the police power. The point is to realize that a police state (i.e. one arising out of or centered around the exercise of the police power) is not an ordinary form of government and that police (contrasted with sheriffs, de jure conservators of the peace, de jure justices of the peace or coroners) are a lower order of law enforcement. And, for what its worth, the shrieval power is princely or royal power....the direct control of civilians by military personnel operating in those territories where civilians are present, but no effective (or even any) civilian government exists.
As I pointed out on another thread, when this kind of change happens, the shrieval power is typically removed from participation in tax collection since the municipal corporation or borough will pay taxes to the King (via an agent such as the county treasurer) directly.
Note there isn't a box labeled 'County', but there is one for 'City'.
It might help to understand the connection with exercise of the police power and revenue/debt/tax collection.
Note: This is posted under Identity for a reason.