The former U.S. attorneys for North and South Dakota have joined a prominent Minneapolis law firm to launch a group focusing on American Indian law and policy practice.

Brendan V. Johnson and Tim Purdon, who served South and North Dakota, respectively, resigned from their offices in March and joined Robins Kaplan. They will work with clients on such issues as commercial and agency disputes, gaming rights, government investigations, personal injury, natural resources and tribal boundary disputes, the firm said in a news release. The practice also will address judicial systems and public safety issues.

"For far too long, American Indian tribes across the United States have faced a competitive disadvantage when litigating powerful forces," Martin Lueck, chairman of the Robins Kaplan executive board, said in the news release. "We are excited to announce the American Indian Law and Policy Practice, where Brendan and Tim, along with a talented internal team, will bring justice to tribal communities."

Johnson had served as U.S. attorney for South Dakota since 2009. During that time, he was selected by U.S. Attorney General Eric Holder to chair the Department of Justice's Native American issues subcommittee and to serve on the attorney general's advisory committee. Johnson was also a member of the Justice Department's terrorism/national security and cybercrime subcommittees.

He developed a community prosecution strategy that helped increase prosecutions by more than 90 percent on South Dakota's largest reservations.

Purdon had served as U.S. attorney for North Dakota since 2010. He implemented the state's Anti-Violence Strategy for Indian Country, which involved putting assistant U.S. attorneys on the reservations on a regular basis to forge ties with tribal communities. The strategy also increased support for crime-prevention and postprison community re-entry programs. It increased prosecutions on reservations by 80 percent.

In 2013, Purdon was appointed by Holder to serve as chair of the Department of Justice's Native America Issues Subcommittee.

"As U.S. attorneys, Brendan and I worked relentlessly to see new ways to improve public safety in Indian County," Purdon said in a news release. "Supported by our talented colleagues, we will bring this same commitment and incisive strategic thinking to our private practice work for the tribes and the citizens of Indian Country."