To add to the very comprehensive reply below/above from @moderator :But as a civvy, can he not just ignore any notice requiring him to go before a Courts Martial?
once a charge has been formulated then it has to be served and the accused has to be allocated a Commanding Officer. It is feasible that any person who states they will not attend may be placed in post-charge custody. Admittedly unlikely in this instance, but it could happen.
If the person charged does not appear then a warrant for their arrest can be issued.