Mack began his career with the Provo Police Department as a parking enforcement cadet while attending BYU. A couple of years later he became a full-time officer and was soon promoted to Corporal, Sergeant, and Detective. His most traumatic experience there was a one-year assignment as an undercover narcotics agent. After nearly 11 years at Provo PD, Mack decided to return to his childhood turf in Arizona and run for Graham County Sheriff. His campaign took off and he was elected in 1988.
He was sheriff for two terms until 1997. He was named Elected Official of the Year by the Arizona-New Mexico Coalition of Counties in 1994, received the NRA Law Officer of the Year, inducted into the NRA Hall of Fame, 1995 Cicero Award, Samuel Adams Leadership Award from the Local Sovereignty Coalition, and Gun Owners of America Defender of the Second Amendment Award.
During his tenure, federal officers informed the sheriffs of the state that they would be required to enforce the so-called “Brady Bill” and run background checks at their expense under the law. In 1994, Mack and six other sheriffs from across the country, challenged the constitutionality of the Brady Billand ultimately, fought it all the way to the United States Supreme Court, where they won a monumental decision for freedom.