Hours after the nation’s first execution by nitrogen gas in January last year, Alabama's attorney general urged other states to also develop it as a method for carrying out death sentences. Now, some states are following suit.

A death row inmate slated to become the first person to be put to death by nitrogen gas in Louisiana is seeking to halt the execution, citing constitutional concerns over the controversial killing method.

Louisiana officials have unsealed a redacted version of the state’s execution protocol for nitrogen hypoxia, providing the first public look at how the state plans to carry out its first execution in nearly 15 years.

Arkansas currently only allows executions by lethal injection. If this bill becomes law, the state would join a small group of others permitting nitrogen hypoxia.