Roy Moore, a Republican vying for his party’s nomination in the special election for a U.S. Senate seat in Alabama, is touting the endorsement of an anti-choice activist who once signed a letter endorsing the murder of abortion care providers as a “justifiable” act.

The endorsements listed on Moore’s campaign website list the Rev. Matt Trewhella as a key supporter of the Alabama Republican’s Senate bid, as People of the American Way’s Right Wing Watch first reported.

“Trewhella has long been an activist on the far fringes of the anti-choice movement,” Right Wing Watch’s Miranda Blue wrote. “In the early 1990s, he was one of 34 anti-abortion extremists to sign a statement declaring that the murder of abortion providers is ‘justifiable.’ Another signer of the statement, Paul Hill, went on to murder an abortion provider and the provider’s bodyguard. Around that time, Trewhella was videotaped calling for churches to arm children in order to form militias.”

Moore’s campaign site identifies Trewhella as the “author of ‘The Doctrine of the Lesser Magistrate.’” In a blog post for what is his website of the same name, Trewhella defended President Trump’s notorious suggestion on the campaign trail that women who have an abortion should face “some form of punishment” should the medical procedure be made illegal, calling it a “no brainer.” 

“If abortion is murder—and it is—the woman should be punished,” wrote Trewhella, going on to suggest abortion is a “capital crime.”

“When we are asked what the punishment should be for women who have illegal abortions, we should unashamedly respond—whatever the penalty is for murder in the state where it takes place,” he wrote.

Trewhella served time in jail for actions associated with his anti-choice activism, as Rewire reported. He co-founded the anti-choice group, Missionaries to the Preborn, and was “one of a half dozen anti-abortion activists [then] under investigation as possible conspirators in a campaign of violence against abortion clinics,” according to an August 1994 report from Newsweek.

Though Trewhella later removed his name from the aforementioned statement suggesting that the murder of an abortion doctor was “justifiable,” he nonetheless “was a mentor for potentially violent anti-abortion extremists” according to a Newsweek investigation.

Trewhella is a part of an arm of the anti-choice movement advocating that states ignore federal law and court decisions that safeguard abortion rights. Moore has twice been removed from his position as a justice on Alabama’s Supreme Court, including once for refusing to comply with the U.S. Supreme Court’s landmark marriage equality decision.

Moore has numerous ties to anti-choice extremists, including Operation Save America, according to another report from Right Wing Watch. The anti-choice group’s leader, Rusty Thomas, has donated to Moore’s campaign, and Moore has spoken to the group’s supporters and accepted an award from it.

The campaign’s website notes endorsements from anti-abortion radicals, Operation Rescue’s Troy Newman and Personhood USA’s Jason Storms.

Moore faces Sen. Luther Strange in Alabama’s runoff for the Republican nomination for the special election for U.S. Senate on September 26. The winner will face Democrat Doug Jones in the December general race.