I think this answers the question on McGregor’s authority

e Civil War Message Board

Militia men of 1861
By:Damon Cluck
Date: 7/6/2016, 10:36 am
Daily Arkansas Gazette (Little Rock, Arkansas) 13 November 1904, Sunday, Page 5, https://www.newspapers.com/image/132666255/?terms=arkansas%2Bmilitia

"Among the discoveries being made by MAJ, S. H. Nowlm, compiler of the military records of the civil war, is a record book which was furnished him by Wm. H. Cornwall of this city, who is one of the clerical force of the Iron Mountain shops at Baring Cross. This book contains the original records and orders issued at the beginning of the war and prior to an transfer of Arkansas troops to the Confederate service. and the roster of companies which comprised the second division of Arkansas militia.

The first order of the commander-in-chief and governor of the state is as follows

Headquarters, Arkansas Militia, April 26, 1861

General James Yell-Will Repair immediately to Hopfield and rendezvous as many troops from his division of the Arkansas Militia as in his opinion are adequate to security and defense of the eastern portion of Arkansas. Every discretion necessary to successful defense is given to you, with full power to call out troops and erect batteries, etc, commensurable with this object. It is important that the commander-in-chief should be advised daily of by your adjutant of the plan and progress of operations. Respectfully,

"Henry H. Rector
"Commander in Chief Arkansas Militia."

There were five companies mustered in to service. Two were as follows:
Jefferson Guards, received into service April 27, 1861:
Captain, C.H. Carlton.
First lieutenant L. donelson
Second lieutenant Griff Bayne
Third lieutenant J.W. Bradford
Orderly sergeant, J.R. Holland.
Privates.......

Pine Bluff Artillery, received into service April 27, 1861:
Captain F.P. Steck
First lieutenant. S.B. Reeder
Orderly sergeant, Ben Barnes.
Privates.....

Next Sunday's Gazette will contain the original rolls , under this muster of April 1861, or the following companies:
Yell Rifles, P.R. Clayburn (sic), captain
Boarder Rangers, D.M. Rae (sic), captain
Hindman Buards, H.B. Blackemore, captain
The staff of General James Yell