Yes, it is illegal (because of the auto-deleting messages) and explicitly against the rules that every one of these people mandates for their own employees. All

Yes, it is illegal (because of the auto-deleting messages) and explicitly against the rules that every one of these people mandates for their own employees. All of them know that federal records must be preserved, and you have to manually turn on Signal's auto-deletion feature, so this is obviously intentional criminal activity.