Amnesty International's study, Maze of Injustice, finds that Indigenous women in the US face sexual violence at a far higher rate - as many as one in three - than the general population.
However, tribal law enforcement agencies are chronically underfunded by federal and state governments.
Due to complicated jurisdictional arrangements between tribal, state, and federal law enforcement agencies, it's often unclear who has jurisdiction, and response time is compromised.
As many as 86% of reported cases of rape against indigenous women are committed by non-Native men. This is a continuation of the historical violence against indigenous women, perpetrated by settlers and soldiers as a means of subjugation. Tribal courts cannot try cases against non-Natives (and can only impose punishments up to one year in any case), but the majority of the cases they refer to Federal prosecutors are reportedly never brought to trial.
A summary of the report is available here. A slide show, which is probably a better summary, is here. The full report is here.
The United States has historically perpetrated violence against Native women, and has failed to stop it. Amnesty International is asking that people urge their Congresspeople to fully fund the Violence Against Women Act, including Title IX, the Tribal Title.