The Justice Department reports that one in three Native women is raped over her lifetime, while other sources report that many Native women are too demoralized to report rape. Perhaps this is because federal prosecutors decline to prosecute 67 percent of sexual abuse cases, according to the Government Accountability Office. Further tearing at the social fabric of communities, a Native woman battered by her non-Native husband has no recourse for justice in tribal courts, even if both live on reservation ground. More than 80 percent of sex crimes on reservations are committed by non-Indian men, who are immune from prosecution by tribal courts.

The Minnesota Indian Women’s Resource Center says this gap in the law has attracted non-Indian habitual sexual predators to tribal areas. Alexandra Pierce, author of a 2009 report on sexual violence against Indian women in Minnesota, has found that there rapes on upstate reservations increase during hunting season. A non-Indian can drive up from the cities and be home in five hours. The tribal police can’t arrest him.

To protect Native women, tribal authorities must be able to apprehend, charge and try rapists — regardless of race. Tribal courts had such jurisdiction until 1978, when the Supreme Court ruled that they did not have inherent jurisdiction to try non-Indians without specific authorization from Congress. The Senate bill would restore limited jurisdiction over non-Indians suspected of perpetrating sex crimes, but even this unnerves some officials. “You’ve got to have a jury that is a reflection of society as a whole, and on an Indian reservation, it’s going to be made up of Indians, right?” said Senator Charles E. Grassley of Iowa, the top Republican on the Senate Judiciary Committee. “So the non-Indian doesn’t get a fair trial.”

Leaving aside the fact that most Native defendants tried in the United States face Indian-free juries, and disregarding the fulsome notion that Native people can’t be impartial jurists, Mr. Grassley got his facts wrong. Most reservations have substantial non-Indian populations, and Native families are often mixed. The Senate version guarantees non-Indians the right to effective counsel and trial by an impartial jury.

Tribal judges know they must make impeccable decisions. They know that they are being watched closely and must defend their hard-won jurisdiction. Our courts and lawyers cherish every tool given by Congress. Nobody wants to blow it by convicting a non-Indian without overwhelming, unshakable evidence.