You are free to contradict. I still contend, and admit I am not familiar with the pertinent documents in British service, that here in the US the governing document for courts martial is the Uniform Code of Military Justice. Note that this is not a law per se in the US but a codification of other US laws in a form unique to the military.
As can be seen by; " Authority: E.O. 12473; 10 U.S.C. 47.
Source: 68 FR 36916, June 20, 2003, unless otherwise noted.
Sec. 152.1 Purpose.
This part:
[[Page 569]]
(a) Implements the requirement established by the President in
Executive Order 12473 that the Manual for Courts-Martial (MCM), United
States, 1984, and subsequent editions, be reviewed annually.
(b) Formalizes the Joint Service Committee (JSC) and defines the
roles, responsibilities, and procedures of the JSC in reviewing and
proposing changes to the MCM and proposing legislation to amend the
Uniform Code of Military Justice (UCMJ) (10 U.S.C., Chapter 47).
(c) Provides for the designation of a Secretary of a Military
Department to serve as the Executive Agent for the JSC.
Sec. 152.2 Applicability.
This part applies to the Office of the Secretary of Defense, the
Military Departments (including the Coast Guard by agreement with the
Department of Homeland Security when it is not operating as a Service of
the Department of the Navy), the Chairman of the Joint Chiefs of Staff,
the Combatant Commands, the Inspector General of the Department of
Defense, the Defense Agencies, the DoD Field Activities, and all other
organizational entities in the Department of Defense (hereafter
collectively referred to as ``the DoD Components'')."
This MCM and the UCMJ by extension are based on executive order and federal regulations. Which are also not laws, though grounded in them.