I stumbled upon the Wikipedia article on the kingdom of Nri randomly a few months ago. In it it is claimed that "The kingdom was a haven for all those who had been rejected in their communities and also a place where slaves were set free from their bondage." and "Nri expanded through converts gaining neighboring communities' allegiance, not by force."
These claims make Nri out to be some kind of utopia - and while I would be happy to believe such a utopia had existed at some point, it also seems a bit too good to be true. Especially since none of the claims are sourced. Similar claims seems to be made on some other sites like this one: https://sites.psu.edu/afr110/2014/09/24/kingdom-of-nri-the-history-of-nigeria/ but the claims aren't sourced here either (it seems to me. To be honest I'm not that great at navigating websites)
So my question is - do we really know if this was the case? Is the history of Nri politicized in any way? Are these claims outright lies, misinterpretations or true?
The model is not unknown elsewhere in West Africa when people were the deeply limiting factor; Akan forest city-states grew in part through the progressive incorporation of formerly enslaved people. The idea that after the tenth king of Nri, any slave who set foot there was immediately free, most commonly comes in recent years from Douglas Chambers's essay ("Tracing Igbo into the Diaspora") in Paul Lovejoy's edited Identity in the Shadow of Slavery (2000) which is visible on his Academia.edu profile if you're registered. For the specific point, Chambers cites back to M. A. Onwuejeogwu's 1981 An Igbo Civilisation: Nri Kingdom and Hegemony, which is a book I don't know and don't have access to, but you may wish to look into that.
Such works as Onwuejeogwu's often draw on oral history as well as archaeology with a greater degree of license befitting someone who is truly fluent in the culture and language. So the question about whether or not it was strictly empirically true in the manner you've seen it presented is a valid one. Certainly, those in the Nri area had much to gain by foregrounding such a policy, and I doubt any would suggest that others didn't raid Nri. But because Nri is seen as the founding entity for Igbo identity by at least some people the stakes would be that much higher. I am not, however, aware of any scholarship that takes issue with the claim. That does not mean there isn't any, because there is a wide world of Nigerian scholarship that never gets play in European or North American presses because of the old vicious cycle (no market, therefore no publisher, therefore no market, therefore no publisher, etc).
I will have another look once I am feeling well (got the current ick) and can get to my office to look at Foundations of Nigerian History and a few other West Africa published volumes.