Dr. Demento, The argument you make is European colonial argument and is incorrect.

The Canadian court system was not established by the indigenous people, it was by the colonizers of Indigenous territories. It serves a purpose of supporting colonial interests, through the colonial laws it uses to seek judgements. The court system played a massive role in the dispossession of Indigenous lands and waters by colonizers, and continues this role by refuting Indigenous claims to their lands and waters. 

Please note, the many treaties (written documents) that are not lived up to by the colonizers and ignored by courts.

The indigenous cultures of Turtle Island are oral cultures. Histories are handed over from generation to generation, the accuracy secured by, internalizing through repetition, number of keepers, and public reciting. It is simply a different way of recording history. To suggest that only 'written documents' have legal value, suggests Western European arrogance and ignorance.