I’m thinking the Marines are for localities where the local authorities decline to cooperate with Federal law enforcement.
Cnador7 and I have been having a little discussion about this on the thread about it, your comment would fit right in and makes sense and was sort of what I was trying to say after this but you said it better:
MANPOWER GUIDANCE FOR ACTIVATION AND DEACTIVATION OF RESERVE COMPONENT (RC) MARINES
http://www.freerepublic.com/focus/news/3783773/posts?page=51#51