Sioux Nation of Indians was not, ultimately, whether the United States had taken the Black Hills.

By 1980, that was not seriously disputed.

The question was whether the taking had been done in good faith, in pursuance of Congress’s power to manage tribal property for the benefit of the tribes — or whether it had been a straightforward seizure that implied an obligation to compensate.

The legal framework the Court applied was what it called the “good faith effort” test, drawn from earlier cases.

The test asked whether Congress, in taking tribal land, had made a genuine effort to provide the tribe with fair value for what was taken.

If Congress had acted in good faith — had genuinely tried to compensate fairly — the action might be characterized as a legitimate exercise of the government’s fiduciary power over tribal affairs, not a compensable taking.