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Utah lawmakers on Tuesday approved a measure that would make firing squad the method of execution in the state if authorities can't obtain increasingly scarce lethal injection drugs.

Before the 18-10 vote by the state Senate, Gov. Gary Herbert declined to say explicitly if he would sign the bill but noted that Utah is having trouble finding chemicals to kill death-row inmates.

"If those substances cannot be obtained, this proposal would make sure that those instructed to carry out the lawful order of the court and the carefully deliberated decision of the jury can do so," Herbert, a Republican, said in a statement.

There are a handful of inmates on Utah's death row who can already choose firing squad as their execution method because they were sentenced before 2004, when the state took that option away. The last prisoner to be executed by firing squad was Ronnie Lee Gardner in 2010.

Randy Gardner told NBC News that his brother — who was sentenced to death for killing a lawyer in court while facing charges for a previous murder — opted to be shot by his executioners because he believed it would stir opposition to capital punishment.

"It's not humane at all," Randy Gardner said of firing squads. "I got to see the four bullet wounds in my brother's chest after the execution and I could have put my hand in there. It's cruel and unusual punishment for sure."

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Utah is one of several states that have turned to alternate execution procedures because pharmaceutical companies have stopped selling their products to prisons for capital punishment. Tennessee brought back the electric chair as a backup last year, but inmates have sued to stop it from being used.

"We have to have an option," Utah Rep. Paul Ray told reporters when he introduced the House version of the firing squad bill.

If the governor signs the bill, any attempt to use a firing squad is certain to come with a court battle. There are nine inmates on Utah's death row right now and no scheduled executions.

A raft of executions across the country are on hold either because the states cannot find the drugs or because inmates are challenging the chemicals in the protocol.

The U.S. Supreme Court has agreed to hear an appeal next month that will determine if three states can continue to use a sedative called midazolam as the first agent in a three-drug cocktail despite claims it doesn't protect inmates from excruciating pain.

A poll commissioned by NBC News last spring, in the wake of a badly botched lethal injection in Oklahoma, found Americans are open to alternatives if the needle no longer becomes a viable way to carry out the death penalty.

Twenty percent of those polled expressed support for the gas chamber, 18 percent for the electric chair, 12 percent for the firing squad and 8 percent for hanging.

Last July, a federal appeals judge said lethal injections are a "misguided" effort to mask the brutality of executions and suggested a method most closely associated with the French Revolution would be better.

"The guillotine is probably best but seems inconsistent with our national ethos," Judge Alex Kozinski of the Ninth U.S. Circuit Court of Appeals wrote in a dissent at the time.

"And the electric chair, hanging and the gas chamber are each subject to occasional mishaps," he continued. "The firing squad strikes me as the most promising. Eight or ten large-caliber rifle bullets fired at close range can inflict massive damage, causing instant death every time."

Utah has used the firing squad three times, most famously on Gary Gilmore, the subject of Norman Mailer's "The Executioner's Song," who was the first person put to death in the U.S. after the Supreme Court reinstated capital punishment in 1976.