Generally, police services like the RCMP, the Sûreté du Québec, the Ontario Provincial Police or the Indigenous police forces themselves, are in a position to enforce the Criminal Code in Indigenous communities. That is not a problem. However, it becomes more of a problem in cases that are not within the responsibility of the police services. Some band council regulations are not of the same type as those that police services generally enforce, in the same way as some municipal, provincial or federal regulations are not enforced by police services.
However, I invite you to discuss the issue with an Indigenous police chief or a member of the RCMP. They would be able to describe the kind of operational problems they face on the ground.
I hope that answers your question.