Herbert has said he finds the firing squad "a little bit gruesome," but Utah is a capital punishment state and needs a backup execution method in case a shortage of the drugs persists.

"We regret anyone ever commits the heinous crime of aggravated murder to merit the death penalty, and we prefer to use our primary method of lethal injection when such a sentence is issued," Herbert spokesman Marty Carpenter said. "However, when a jury makes the decision and a judge signs a death warrant, enforcing that lawful decision is the obligation of the executive branch."

The measure's approval is the latest illustration of some states' frustration over bungled executions and difficulty obtaining the drugs.