Eh - here we go, all caught up in another layer of illusion.
Can a non-native (anything) be a shaman? Can a non-european be a practicing druid?
Why are we putting these labels on beautiful and life-enhancing practices?
The GreatSpiritMotherGoddessGrandfatherMantis (add in whatever god of whatever aboriginal culture you prefer) doesn't give a DAMN what color skin the person acknowledging them has, because each and every one of them is the same exact thing - interpreted differently by different cultures in different times and places. If we allow ourselves to get wrapped up in what we "can" and "can't" adopt into our spiritual lives we are going to live very poor in spirit.
I understand that various and assorted aboriginal and native peoples of various lands hold it against white europeans for having taken away their lands and cultures, but for anyone, regardless of color or heritage, to say that a person can't adopt a native practice or belief system because of the color of their skin or their heritage, is to have completely missed the point that their traditions were/are teaching.