Peterson worked from 1975 until 1978 as an instructor with the Grand Forks, North Dakota Park District and from 1979 until 1983 as a graduate teaching assistant at the University of North Dakota. From 1984 until 1988, Peterson was a lecturer at the University of North Dakota's Department of English. During law school in 1989, she served as a judicial extern for North Dakota Judge Bruce Bohlman, and then in 1990 she served as a legal extern for United States SenatorKent Conrad. From 1991 until 1993, Peterson served as a staff attorney for United States District Court for the Eastern District of Washington Judge Frederick L. Van Sickle.[4] Peterson then worked as an associate attorney for a Spokane law firm from 1993 until 1994 and then was a sole practitioner in 1995. She then served as an associate attorney for another Spokane law firm from 1995 until 1997, and then was partner in a different Spokane law firm from 1998 until 2002. From 1999 until present, Peterson has served as an adjunct professor (1999–2005), a visiting professor (2005–2007) and an assistant professor (2007–2010) at the Gonzaga University School of Law. She became the director of the law school's externship program in 2002.[4][3]
In 2015, Peterson became a central figure in Second Amendment and Tenth Amendment protests in Spokane. Following the arrest of Anthony P. Bosworth on February 25, 2015,[7] Peterson authored new rules banning firearms and other weapons on the grounds surrounding the Thomas S. Foley Federal Court in Spokane.[8] Bosworth's arrest and detention on February 25 led to an additional protest on March 6, 2015, where a large crowd defied the judge's order by appearing armed on the Foley Courthouse plaza.[7]
In 2019, Peterson made national headlines when she blocked the Trump Administration from implementing its changes to the “public charge” rule nationwide.[9]