My thoughts would be to enable/disable wireless access to systems via using a MAC Address Filter. This would be a process where you only approve devices with specific mac address to connect to your wifi. And when you no longer want one of them to have internet access you simply remote into the router and remove or disable the checkbox for the mac address that is in relation to the computer that you no longer want to be on the network. This would require you to probably follow up with this change with a manual reset option which most routers have in their web gui interface. Upon reset of the router that one laptop or desktop with wifi will no longer have an internet connection.
I am trying to figure out why you want to do this? What is the real problem that is not described here?
If this is a parent wanting to shut off internet access to a childs computer, some routers have where you can set them to only have connection between router and computer between specific hours of the day. * However the kid hack to this is a paperclip if the kids have access to the router and can perform a hard reset back to factory default of everyone having unlimited internet connections.
In my home I installed 2 wireless routers. One of which is on a $6 wall timer and so this 2nd $20 wireless router is only functional for certain hours of the day. And this wireless router is the one that my daughters computer connects to, so that she cant wake up at 3am and decide to game on the internet while we are sleeping. The wall timer that she is unaware of makes this router live from 3pm to 9pm and then it shuts off. Meanwhile my wireless router is on 24/7 but she doesnt have the key to connect to it.
To shut a router off to pause it for a while and then have it come back on or active again from pause, there are Web Power Controllers out there for around $90 -$130 that allow for this. I used some DLI Web Power Controllers to allow myself to remotely power cycle devices that were prone to be troublesome with lock ups etc, such as a private Copperlink DSL connection through a burglar alarm circuit ( leased copper pair ) point to point through telephone company that allowed us to have a private DSL 4mbps network bridge to other offices within 5 miles. The problems with these modems were that lightning storms would make them lock up even if you had UPS's at both ends powering the modems. The Electromagnetic radiation from lightning would cause them to lock up even when lightning never struck the line that they were connected to through a weak EMP.
Here is the devices that I used to remote admin ( power reboot ) equipment from home or from other sites at my prior career where I was systems admin. They worked sweet!!!
http://www.digital-loggers.com/lpc.html