Ohio Governor Mike DeWine is dismissing a lawmaker’s proposal to use fentanyl to execute death row inmates as the state struggles to find a lethal injection method.

The Columbus Dispatch reports the Republican governor says the powerful synthetic opioid, which has led to thousands of fatal overdoses in Ohio, isn’t an option and likely would not pass “constitutional muster.”

Rep. Scott Wiggam, a Wooster Republican, is seeking co-sponsors for a bill to use fentanyl seized by law enforcement agencies for executions.

DeWine canceled the execution of convicted killer Warren Henness in January after a federal judge expressed concerns about Ohio’s lethal injection protocol.

Nebraska used fentanyl obtained from a pharmacy to execute a prisoner last year.