You can apply different network policies to different APs, and then you could control which devices connected to which AP. If all of the APs are using the same network policy, we don't have a way to prevent clients connecting to one AP over the other. You could also disable SSIDs on certain APs, so they'd be using the same network policy but there would be no SSID for the client device to connect to, so it wouldn't connect to that particular AP.
Could you elaborate on why you're trying to restrict client access to particular APs? If I know more about what you're trying to accomplish, I might be able to give you better feedback.
