Back in the early years of AH, the AH community would police itself on this particular issue
Some other options to possibly help these days
1- if a friendly dives infront of another friendly to kill steal, and causes the friendly they are killing stealing from to take damage, should get a system warning if they cause small damage or
1 strike - first time they causes friendly to killshooter with warning that if they do it again they will be png (person-non-grata) and are grounded with a time out for 10, 20, 30 minutes or more! Regardless if they are switching countrys by using the recent "auto country switching to help keep sides balanced " option that was added
2 - if they cause 2 (or 3) to kill shoot themselves , they are sent a message that they are grounded for 12 hours or something
Just some thoughts
TC