Enabling policy in a custom environment

This may be pretty esoteric, but I have an Istio environment for which I want to enable policy checks. The official documentation says:

“Execute the following command from the root Istio directory”: istioctl manifest apply --set values.global.disablePolicyChecks=false

But unfortunately, this is a custom environment and I don’t have an Istio install directory. Is there another way to apply this config change to the running Istio environment without having Istio config files?