"Lieutenant. By edict of Confederate High Command, all matters regarding these xenomorphs are under Class 7 Seal. Do not speak of the existence of the xenomorphs or in any way relay the events surrounding their appearance on Chau Sara. Failure to comply with these orders will result in immediate termination. This conversation never took place. We were never here."
A class 7 seal was an edict produced by Confederate High Command. It enabled the lockdown of an entire topic or incident, preventing any flow of information. Failure to abide by the law would result in "immediate" termination.