U.S. Supreme Court Justice Sandra Day O'Connor, whose centrist voice made her a powerful player in a slew of Indian law cases over the past 25 years, resigned on Friday, paving the way for what is expected to be a high-stakes battle over a replacement.

O'Connor, 75, the first woman appointed to the high court, offered few words in her resignation letter [PDF]. "It has been a great privilege, indeed, to have served as a member of the court for 24 terms," she told President George W. Bush, who doesn't plan on naming a successor until next week at the earliest.

A nominee of the late president Ronald Reagan, O'Connor's 24 years on the bench were marked by a dramatic shift in the federal judiciary's view of Indian Country. Tribes used to look to the court to affirm their sovereignty, land and treaty rights but began to lose major cases, starting in the 1980s.

"In recent years, that has changed as the U.S. Supreme Court, and the federal courts generally, have gotten a bit more conservative on us and it hasn't been as easy as it used to be to win these cases," John Echohawk, the executive director of the Native American Rights Fund, said at a recent conference.

While appointed by a staunch Republican, O'Connor defied labels when it came to the court's Indian docket. She authored major decisions in favor of tribes, occasionally blasted her colleagues for taking a limited view of tribal sovereignty and often provided the "swing" vote in close decisions.

A critical case from the October 2000 term, in which tribes lost five out of six cases, is illustrative. In Nevada v. Hicks, she defended tribal self-determination amid a series of conflicting and confusion opinions written by her fellow justices.

"The court holds that a tribe has no power to regulate the activities of state officials enforcing state law on land owned and controlled by the tribe," she wrote on June 25, 2001. "The majority's sweeping opinion, without cause, undermines the authority of tribes to 'make their own laws and be ruled by them.'"

In the courtroom, O'Connor was equally forceful. She was almost always the first justice to ask questions during oral arguments for Indian law case, an area with which she was intimately familiar. She practiced law and served as a judge in Arizona, home to 21 tribes.

During the hearing for US v. White Mountain Apache Tribe, the Department of Justice lawyer barely got out one sentence before being interrupted. O'Connor posed a key question about the federal government's management of an historic fort held in trust for a tribe in her home state.

"What condition was it in, in 1960?" she asked on December 2, 2002. "Was it basically like it is today, or has it gotten worse? What was it like then?"

The court later ruled, in a 5-4 decision with O'Connor providing the swing vote, that the U.S. violated its fiduciary obligation to the tribe by allowing the trust property to fall into waste.

O'Connor also came down on the other end of the stick during her tenure. In Lyng v. Northwest Indian Cemetery Protective Association, issued on April 19, 1988, she ruled that the federal government could build a road through a sacred site over the objections of California tribes. The vote was 5-3, with Justice Anthony Kennedy not participating.

In South Dakota v. Yankton Sioux Tribe, she authored the unanimous opinion, holding that the Yankton Sioux Tribe of South Dakota lost the majority of its reservation. Despite the negative decision, she found ways to respect tribal rights, a characteristic not always found in the writings of her colleagues.

"The allotment era has long since ended, and its guiding philosophy has been repudiated," she observed on January 26, 1998. "Tribal communities struggled but endured, preserved their cultural roots, and remained, for the most part, near their historic lands."

Years later, she took part, along with Justice Stephen G. Breyer, in an historic trip to three reservations. During a stop on the Navajo Nation, she said was "very impressed" with the tribe's "peacemaker" court and how it approached problems in non-confrontational way.

O'Connor plans to leave the court once her replacement is confirmed by the Senate. Republicans and Democrats, and their supporters, are already gearing up for a major battle. The parties have been at odds over Bush's federal and appeals court nominees, leading to filibusters against some considered too extreme by Democrats.

The White House has been tight-lipped about a nominee but news reports have speculated that Bush might pick an appeals court judge or an administration ally. One of the names most often cited is Judge John G. Roberts Jr., 50, who was recently confirmed to the D.C. Circuit Court of Appeals. He has had significant experience in Indian law, having argued two critical cases during O'Connor's tenure.

From the Indianz.Com Archive:
O'Connor defends tribes amidst squabbling (June 26, 2001) | State officials barred from tribal suit (June 26, 2001)

Relevant Links:
NARF-NCAI Tribal Supreme Court Project - http://www.narf.org/sct/index.html