Martial law and or Martial Rule are branches of the law of war, which is a branch of the law of nations which is Roman based international law; Justinian's code and regulation which has been in effect since April 15, 1861. The U.S. CODE sits under the Lieber Code and not the "We the People" constitution?
Congress sits under the commander-in-Chief as do the STATES, COURTS and all LAW enforcement.
If Lincoln and those who came after him did away with the common law what was put in its place?
The answer here is Roman based law represented in the Codes of Justinian.