If he's really inactive, he will autopause.
Why do you need to get rid of him? If there's something specific you need him to do, give him an order. If he's just logging in often enough not to auto-abdicate, and not checking messages, he'll fail to follow the order, and you can ban him after a while.
If he reads the message, and follows the order, then you don't really need to get rid of him.