You provided a lot of information, but not certain specifics that may help others find information in this case.

What is the name and place of residence of the brother-in-law who transported medical supplies to the South? Perhaps we can find his prison or tribunal or Provost Marshal information from those missing facts.

Tell us more about Colonel Robert M. Renick, especially where he lived (by town and county). In what war did he earn the rank of colonel?
How do you know he was a "high-ranking member of the Knights of the Golden Circle"?

The MO Secretary of State's Office online military service records from the Missouri State Archives do state that that E. A. Corbet at age 45 was given the rank of captain of Company F, 16th Enrolled Missouri Militia as of or shortly after his enrollment (as required by state law) on 3 September 1862, at the beginning of the EMM program. Corbet may have been elected to his captaincy by the men he commanded. The 16th EMM was called a "contractors" regiment and was located in the St. Louis area (there were about 23 more or less full regiments in the St. Louis area, and some of them were for firemen, some for policemen, and others like the rural EMM units only had in common that all members lived in a certain geographical location, such as a county. One of the outstate EMM regiments was only for guarding one of the Missouri railroads, and was called the "railroad regiment." The St. Louis area EMM units did not provide the kind of hard service that the rural ones performed, but they did drill and perform guard duty and may have assisted the provost marshal's office with arrests, handing suspects, and the like. I don't know if any of the "city" regiments served on patrols or scouting, but perhaps some did. Corbet's record shows only the one record it states is from his first "muster-in roll," but with this being more of a ceremonial outfit since it contained all or mostly government contractors, perhaps that is all that was expected of these men. Perhaps that is why the MO Adjutant General's reports for the years 1864 and 1865 skip from the 13th EMM to the 26th EMM and fail to mention a lot of the St. Louis area EMM regiments.

Bruce Nichols