Non-aggression pact with Orks and Eldar

I was watching Luetin's lore video, and at one point he mentions that during the time of human expansion, humans were so strong and what not, that even Orks and Eldars had non-aggression pacts with them.

I could understand Eldar, but how would non-aggression pact with Orks even look like or for that matter, work?