I found it on the wiki before, but now I find it
You can disable the users input by removing the HumanoidController and instancing a new one when you need to enabled the movement.
Disable users input:
game:GetService("ControllerService"):ClearAllChildren()
Enable users input:
Instance.new("HumanoidController", game:GetService("ControllerService"))
I'm not sure if you can completely disable the keys, but to prevent movement you can Anchor/Lock a characters Torso with a Script, thus preventing them to move.