A former lobbyist for Gun Owners of America, he is known for his role in a successful lawsuit which alleged that portions of the Brady Handgun Violence Prevention Act violated the United States Constitution.

[2] 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.

[6] 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.

[6] Mack ran as a Libertarian candidate for United States Senate in Arizona in 2006 against incumbent Jon Kyl, a Republican, but finished in the general election with 3% of the votes.

In 2012, Mack opposed 13-term Representative Lamar Smith, who introduced and sponsored the controversial Stop Online Piracy Act legislation, in the House election Republican primary for Texas's 21st Congressional district.

[10] Mack is involved in the patriot movement through his role in the Oath Keepers organization and as founder of the Constitutional Sheriffs and Peace Officers Association (CSPOA).

[6] Mack opposes all gun control laws, telling the program News21, "I studied what the Founding Fathers meant about the Second Amendment, the right to keep and bear arms, and the conclusion is inescapable.

"[6] Mack's legal theories that a local sheriff can override federal authority derive from the white supremacist Posse comitatus movement, whose rhetoric he regularly references.