{
  "rules": {
    "users": {
      "$user": {
        "innocent": {
          ".validate": "data.parent().child('on-fire').val() === false"
        },
        ".read": "auth !== null",
        ".write": "root.child('users').child(auth.uid).child('king').val() === true"
      }
    }
  }
}

{
  "rules": {
    "users": {
      "$user": {
        "innocent": {
          ".validate": "data.parent().child('on-fire').val() === false"
        },
        ".read": "auth !== null",
        ".write": "auth !== null && root.child('users').child(auth.uid).child('king').val() === true"
      }
    }
  }
}

Tweak chai example to show new error formatting
Tweak chai example to show new error formatting