According to this https://documentation.meraki.com/MR/Firewall_and_Traffic_Shaping/Wireless_Client_Isolation "With Client Isolation enabled, clients will only be able to communicate with the default gateway and will not be able to communicate with any other devices on the same VLAN (or broadcast domain). In order for the wireless client to communicate with another device, the upstream gateway must be used to enable this communication (Eg Inter VLAN routing and ACLs). Any traffic bound for an address on the same VLAN as a device in client isolation will be denied. Traffic bound for other VLANs will be forwarded and routed normally." So sounds like it may be possible if you are doing inter VLAN. But I haven't tested this so I'll have to defer to other members of the group that use this functionality more often. For our guest networks, I just use "NAT mode: Use Meraki DHCP" when I do not want the clients to be able to talk to each other. When they do need to talk to each other I have a separate network/VLAN.
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