And remember how these taskings work--it starts from the originating civil agency & works it's way up that side and back down the military side to the closest Army installation--in this case Fort Hood. III Corps received the tasking from its boss at FORSCOM, not from the FBI. And there was no option to just say no. This is much ado about nothing in terms of Clark and Army involvement--he wasn't the commander at Hood, but so what if he was? The Army lawfully provided support in the form of equipment and training to civil authorities as required and in accordance with standing procedures.
Your distinction between ADCM & ADCS is lost on me--while their duties differ, they are both equally bound by the same laws. And there is nothing to indicate the military broke any laws.
If Schoomaker was ADCM there is a very high chance that he was involved in the planning. Maneuver is planning. That would have been a clear criminal violation of the Posse Comitatis Act. Support is Support depending on what your meaning of is is.....
So it was made to seem. The only way military equipment and support could have been used legally was in the event of drug interdiction.
It came out in the hearings that exactly none of the personnel in the raid team had taken either the OSHA course in the hazardous chemicals involved in drug-lab seizure, nor had ANY of them taken the course offered by the DEA on how to sieze a Meth lab without having it blow up in your face. It has only been in the last few years that Meth production has utilized pseudoepehdrine and ephedrine containing cold remedies in a different process to produce Meth, the older processes were much more chemically involved and the labs had only a couple of places in the procedure where things could be safely stopped. Otherwise, the evidence would destroy itself. The chemicals involved are dangerous/hazardous/toxic, and the types of releases possible in uncontrolled conditions, especially with gunfire, dangerous also.
The lack of training of anyone on the raid team simply indicates that there was not only no 'Meth lab' as early reports stated, but no possibility of finding one. Keep in mind that the ATF had a snitch in the compound right up until an hour or so before the raid (Koresh let him go), and the picture snaps into focus.
There was no justification for the use of military hardware on either the initial raid or during the seige, in fact, it was illegal.