We recently updated the games with a option requested from us by Server Admins. This option allows the server to detect if an account has Vac bans on record (and how many) and kick the player from the server. Similar options are in several other games on Steam (but are provided by the community). It is turned off by default and admins must choose to enable it (and it has options to ignore a set of bans on record if they choose, such as ignoring one or two bans).
We have had some reports of the system still being enabled when not enabled by the admin and we will be looking into that on Monday. We also may be looking into more options for admins to use in the future (it may be possible for us to add more settings for granular control in the future).
Edit - I am locking other threads and directing the conversation here so I can more easily keep track of it and give the feedback to the rest of the dev team. KEEP THE CONVERSATION CIVIL and try not to antagonize any side taking part or I will remove you from the discussions for awhile.