Ok smart guy... Who issues and enforces the MCM? If you don’t know what it is, or who issues it... Maybe you aren’t as up to speed as you think you are.
The Manual for Courts-Martial (MCM) is the official guide to the conduct of Courts-martial in the United States military. An Executive Order of the President of the United States, the MCM details and expands on the military law in the Uniform Code of Military Justice (UCMJ). The MCM contains 5 parts plus 27 appendices.
Simple enough.
To understand Judge Lind's ruling, one has to understand the defining role of Congress in the military. Hint: it's statutory, as in authorizing, as in what makes certain things legal and other things not. That Constitutional role interacts with the President's Constitutional role in sometimes complex ways.