When automating large changes to your system, the WHM API can be used to simplify and speed up bulk interactions with your server. Below is a reference for the structure of the WHM API call to adjust Reseller ACLs.
From the command-line as root, you can run the following command to update the ACLs for a given Reseller:
whmapi1 setacls reseller='username' acl-disallow-shell=1
More information on the setacls API can be found in our documentation: