Apply firewall rules to an HTTP load balancer

I'd like to take advantage of the Google Cloud Platform HTTP(s) load balancer, but I need to restrict access to the load balancer to a specific block of IP's. Is it possible to apply firewall rules to a GCP HTTP(s) load balancer?

At the moment it is not possible to set firewall rules over the GCE Load Balancers. Nevertheless there is a feature request in place. Since the original source IP is re-written by the LB, you can use the X-Forwarded-For header to obtain the original client and filter it accordingly on your servers.

As Carlos stated in his answer here you cannot apply firewall rules on Google's HTTP Load Balancer.
But you could set some allow/disallow rules on IP ranges through Google's Cloud Armor Security Policies (Use case / How to) by setting the target on the backend service of an HTTP load balancer.