From Halopedia, the Halo wiki
The Limon-Naxla Exception was an Office of Naval Intelligence directive that ordered all field agents on the planet Reach to ignore or countermand orders from ranking UNSC officers below the grade of secure-clear Captain in the event of the declaration of WINTER CONTINGENCY.
However, the Exception was not a carte blanche for intrabranch insubordination. Field agents were ordered to use logic and common sense to decide whether an advantage would be gained by following orders in a particular situation. If the situation permitted, agents were also encouraged to clearly assert Limon-Naxla privilege when possible; otherwise, agent discretion was in play. This did not change the fact that superior officers could and would file reports on Limon-Naxla Exceptions.