Firewall Rule To Block Non-Teams Accounts From Hosting

You can block non-Teams accounts from hosting within your network by using your Team's websocket API. First, you should configure your office firewall to block the Parsec consumer APIs and whitelist the Parsec Teams API. Next, you need to add the URL to your configuration file on each host.
 
Configure Your Office Firewall 
  1. Deny non-Team usage of Parsec by blocking connections to this domain:
    Block kessel-ws.parsecgaming.com
  2. Allow connections for your team to this domain:
    Allow YOURTEAMID.team-ws.parsecgaming.com
    For example, if your team ID is 1abcdefg, you would configure your network to Allow 1abcdefg.team-ws.parsecgaming.com
  3. (Optional) Block *.team-ws.parsecgaming.com at a lower priority than the Allow rule from step 2. This will ensure that someone cannot sign up for a different team and connect to it from your network.

Parsec App Config
You can set the network configuration option using the override feature using a group policy to distribute across the organization.   
  1. In the app, click on Settings, and then on Network
  2. Click on "edit the configuration file directly" near the bottom of the Network settings page
  3. Add the following line at the end of the file:
    ws_host = YOURTEAMID.team-ws.parsecgaming.com
  4. Save the file and restart the Parsec app