U.S. District Judge Jill Parrish set a March 16 trial date on Thursday in the case challenging a 2014 switch to mail-in voting in San Juan County.
The Navajo Nation Human Rights Commission says mail-in ballots are more difficult for rural tribal voters to receive, and fewer physical polling places means it's harder to get language assistance.
San Juan County officials argue the new voting system has led to higher voter turnout. They say the lawsuit was filed in an effort to control local politics.
The county sits in the Four Corners region and covers the northern tip of the Navajo Nation that stretches into Arizona and New Mexico.