Mack served as Graham County Sheriff from 1988 to 1996. In 1994 he was recruited by the National Rifle Association as a plaintiff in one of nine lawsuits against the Clinton administration over the Brady Handgun Violence Prevention Act. Mack v. United States, a lawsuit against the federal government which alleged that portions of the Act violated the United States Constitution, because they comprised a congressional action that compelled state officers to execute Federal law. These portions were interim provisions until a national instant background check system for gun purchasers could be implemented. In a 5–4 decision, the Supreme Court ruled that the provisions of the Brady Act in question were, in fact, unconstitutional.
Oath Keepers and Constitutional Sheriffs and Peace Officers Association
In 2011 Mack founded the Constitutional Sheriffs and Peace Officers Association. The organization has a mission similar to Oath Keepers, encouraging members to refuse to enforce laws that they believe are unconstitutional. Mack is also on the board of Oath Keepers, a far-right patriot organisation known for its controversial presence during the Ferguson unrest and for supporting Cliven Bundy in his standoff against the federal government. In April, 2014, Mack asserted that as part of the citizen response to the Bundy standoff that the Oath Keepers were "...actually strategizing to put all the women up at the front. If they're gonna start shooting, it's going to be women that are gonna be televised all across the world getting shot by these rogue federal officers." The Southern Poverty Law Center included both CSPOA and Oath Keepers on its list of 1,096 anti-government "patriot" groups active in 2013.
Bundy standoff
Mack was a lead figure in the 2014 Bundy standoff. Part of Mack's involvement was strategizing the standoff.
On December 13, 2014, Mack announced his candidacy for Navajo County Sheriff. In his announcement, he said, "We’re gonna make it a constitutional county and show everybody the blueprint for freedom. And there’s a lot more people running for other offices than me. I just said I’d run for sheriff. We’re going to give this one more try. The election is in 2016. I’m going to be moving there in spring of 2015 so I can start getting ready for this. You have about a year and a half to decide. And I’m dead serious about this. If I can move there, so can you." He lost that election to Democratic incumbent Kelly Clarke by around a 10-point margin.
Law enforcement career
Mack spent eleven years with the police department of Provo, Utah, and then moved back to Arizona to run for Graham County Sheriff in 1988. While serving as sheriff, he attended the FBI National Academy and graduated in 1992.
Personal life
Mack was born in 1952 in Arizona. He is a member of The Church of Jesus Christ of Latter-day Saints and attended Brigham Young University, earning a degree in Latin American studies. In January 2015 he suffered a heart attack and his wife became ill in late 2014. Because he and his wife are self-employed they do not have insurance to pay for their medical bills. As a result, friends of the Macks have started a GoFundMe site on their behalf, asking to donate money to help pay for their medical expenses.