The native vs non-native argument is a side issue. This concept arose for good reason because there is danger in introducing a species (especially predators to a new environment). However this has now got out of hand implying that any organism that enters a new environment does not abide by ecological principles and thus has to be eradicated at all cost. Consequently many millions of dollars are wasted every year in the US “eradicating” non-native species with not one success that I am aware of anywhere. And as you point out because no date was set we see obviously non-native Americans are called Native Americans. In your dispute you are dealing with currently the problem is one of serious desertification blamed on the burros. That habitat concern is the issue having nothing to do with any species. I guarantee, and do so now in writing, that if all the burros are shot desertification will continue. This mistake I made in the 1960‟s when my research “proved” too many elephants were causing similar desertification in a major national parks. We shot some 20,000 and it became worse because I, and the committee of ecologists appointed to review my research and approved, was wrong. Like all scientists we interpreted the data to fit the paradigm of our training. When the US government shot 50,000 sheep to stop the desertification of the Navajo lands it became worse but despite the passage of many years the paradigm remains fixed.