(Los Angeles) Death row inmates in Idaho, a western US state, may be killed by firing squad if lethal injection is not possible, according to a law passed Monday by the local legislature.

Approved by 24 votes for and 11 against by the Senate of this conservative state, the text must now be ratified by the governor.

Idaho would thus become the fifth American state to approve this method of execution, after Utah, Oklahoma, Mississippi, and South Carolina, according to the organization Death Penalty Information Center.

Since 1976 and the end of a brief moratorium on the death penalty in the United States, two men and a woman have been executed in this way — all in Utah — the last being in 2010.

American states that apply the death penalty have the greatest difficulty in obtaining the substances necessary for lethal injection, due to the opposition of pharmaceutical companies who do not want to be associated with the death penalty.

The civil liberties group ACLU denounced the passage of the law as “appalling”, calling the text “archaic”.

“A firing squad is uniquely gruesome…such executions leave lasting scars on all involved,” ACLU Idaho said in a statement.

Those killed by firing squad “are in all likelihood undergoing extreme levels of pain and torture”, the organization adds, citing experts.