Orders or regulations under this Act may provide with respect to the government, discipline and pay of the Army Reserve, and with respect to other matters and things relating to the Army Reserve.

No such order or regulation shall render a man who entered the Army Reserve before the date of the order or regulation liable without his consent to be appointed, transferred or attached to any military body to which he could not, without his consent, have been appointed, transferred or attached if the order or regulation had not been made.