if the user logs in he can change this back to active.
That deoends on how you created the site:
if you creatde the site as user or the user created the site himself, then he can activate and deactivate it.
If you created the site as admin for the user (logged in as admin and not as user while you creatde the site), then the client can not set the site to active again when the admin deactivated it. So what you request here is already implementded, you just created the site as wrong user.