Long Distance Voip Block (LDVB)

I am a private Voip user here in the US. I have international call block as do most private Americans. Since robocalls use Voip and is piggybacked on the internet, we can "ping" the source of the call. If it is longer than "x" milliseconds, it can be assumed it comes from overseas and the call can be dumped. If I had the ability to do this myself, I would do it. This concept is definitely within the range of our technology.