Under the law, those found guilty of a sex offence against anyone under the age of 13 will have to take medication to lower their sex drive before being released from jail.
Administered by tablet or injection, chemical castration involves taking a drug to decrease sex drive and libido, but is usually reversed once it's discontinued. It will be up to a court to decide when it's no longer necessary.
Offenders would be required to foot the bill themselves and anyone who refuses to go through the process may be kept in prison.
Hurst told CBS42 that the bill will apply to sex offenders over the age of 21 that have committed crimes against children.
'They have marked this child for life and the punishment should fit the crime,' he added.
The law means Alabama joins seven other states with so called 'chemical castration' laws, including Louisiana and Florida.