SALT LAKE CITY - Utah became the only state to allow firing squads for executions if lethal injection drugs are unavailable when Gov. Gary Herbert signed a law approving the method, even though he has called it "a little bit gruesome."

The Republican governor has said 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, enforcing death sentences is "the obligation of the executive branch."

The governor's office noted that other states allow execution methods other than lethal injection. In Washington state, inmates can request hanging. In New Hampshire, hangings are a fallback if lethal injections can't be given.

The firing squad also is on the books in Oklahoma - but as a third option to be used only if the courts someday find lethal injection and electrocution unconstitutional. The firing squad could be bumped down even further, to Oklahoma's fourth option, if lawmakers approve a bill that would authorize the use of nitrogen gas as another possible method.

Utah's use of the firing squad carries no such legal caveat. Under the new law, inmates would be executed by firing squad if the state is unable to get lethal injection drugs a month in advance.

The proposal's approval represents the latest example of frustration over botched executions and the difficulty of obtaining lethal injection drugs as manufacturers opposed to capital punishment have made them off-limits to prisons.

The bill's sponsor, Republican Rep. Paul Ray of Clearfield, argued the use of trained marksmen is faster and more decent than the drawn-out deaths that occur when lethal injections go awry - or even if they go as planned.

Ray said he wants to settle on a backup method now so authorities are not racing to find a solution if the drug shortage persists. Ray didn't return messages seeking comment Monday.

Opponents say firing squads are barbaric, with the American Civil Liberties Union of Utah saying the bill makes the state "look backward and backwoods."

Utah lawmakers stopped offering inmates the choice of firing squad in 2004, saying the method attracted intense media interest and took away attention from victims.

Utah is the only state in the past 40 years to carry out such a death sentence, with three executions by firing squad since the U.S. Supreme Court reinstated the death penalty in 1976.

The last was in 2010, when Ronnie Lee Gardner was put to death by five police officers with .30-caliber rifles. Gardner killed a bartender and later shot a lawyer to death and wounded a bailiff during a 1985 courthouse escape attempt.