After law school, Nelson served as a law clerk for Judge Karen L. Henderson of the United States Court of Appeals for the District of Columbia Circuit and for Richard M. Mosk and Charles N. Brower of the Iran–United States Claims Tribunal in The Hague, Netherlands.

[4] From 2009 to 2018, Nelson was General Counsel of Melaleuca, Inc.[4] In July 2017, he was nominated to be Solicitor of the United States Department of the Interior.

Nelson was nominated to the seat vacated by Judge N. Randy Smith, who subsequently assumed senior status on August 11, 2018.

[11] He has served as a council member and co-chair of the General Counsel Committee for the American Bar Association Administrative Law and Regulatory Practice since 2012.

[11] Nelson has been a member of the Idaho Chapter of the Federal Bar Association and the Eagle Rock Inns of Court since 2010.