Care should be taken when configuring SSID block list policies as these policies will apply to SSIDs seen on the LAN as well as off of the LAN from neighboring WiFi deployments. Containment can have legal implications when launched against neighbor networks, and it may harm your own network by increasing channel utilization and potential disrupt clients connecting to your APs. Ensure that the rogue device is within your network and poses a security risk before you launch the containment.
Review the section Overview of Air Marshal Containment to understand how the APs may block the configured SSIDs.
In your place, I would not configure it to block by default, but rather create rules to block in specific cases, such as if they are using the same SSID name as yours.
Even this way you can cause problems for your neighbors connecting to their network.
Never use block by default.
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
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