FLAGSTAFF, Ariz. (AP) – The head of the U.S. Bureau of Indian Affairs, who reached settlements with tribal governments in major cases that alleged mismanagement by the federal government, announced Thursday that he is resigning and will return to New Mexico as a law professor.

Kevin Washburn, a citizen of the Chickasaw Nation of Oklahoma, has been on leave from the University of New Mexico since he was selected in 2012 to oversee Indian Affairs for the federal government. He said issues confronting Indian Country, such as youth suicides, have weighed heavily on him, and he wants to dedicate more time to family.

“The responsibilities are just immense, and the challenges are great,” he told The Associated Press. “Frankly, it’s taken a couple of centuries for the problems to get this bad, and it will take a long time to solve them.”

Washburn cited successes in his tenure including settlements over the bureau’s mismanagement of royalties for natural resources on reservations, the reform of leasing regulations, better coordination with tribes and a push for tribes to take over education of their children.

Interior Secretary Sally Jewell called Washburn a “tireless agent for Indian Country.”

“He is a thoughtful leader who provided a steady hand to modernize Indian Affairs to better serve tribes, which will be felt by generations to come in tribal communities across the country,” she said in a statement.

The National Congress of American Indians said Washburn is a strong voice for Indian Country and will be missed. Washburn’s career includes stints as a law clerk, federal prosecutor and general counsel for the National Indian Gaming Commission. He also taught at law schools in Arizona and Minnesota.

Washburn has been critical of a Republican proposal in Congress that would strip the bureau of authority to grant federal recognition to tribes and leave it solely in the hands of lawmakers. The bill came after the Obama administration relaxed some requirements and sped up decision-making.

Some 566 tribes have federal recognition, and hundreds more want to join their ranks.

Washburn said leaders in Indian Country are closely watching for the outcome of that bill as well as a decision in a U.S. Supreme Court case that could limit tribes’ jurisdiction over non-Indians in civil cases.

Washburn’s last day at the bureau is Jan. 1. The deputy assistant secretary, Larry Roberts, will take over in the interim.