BOISE, Idaho (AP) — Idaho on Wednesday became the first state to enact a law modeled after a Texas statute banning abortions after about six weeks of pregnancy and allowing it to be enforced through lawsuits to avoid constitutional court challenges.

Republican Gov. Brad Little signed into law the measure that allows people who would have been family members to sue a doctor who performs an abortion after cardiac activity is detected in an embryo. Still, he said he had concerns about whether the law was constitutional.

“I stand in solidarity with all Idahoans who seek to protect the lives of preborn babies,” Little wrote in a letter to Lt. Gov. Janice McGeachin, who is also president of the Senate.

Yet he also noted: “While I support the pro-life policy in this legislation, I fear the novel civil enforcement mechanism will in short order be proven both unconstitutional and unwise.”

The law in the conservative state is scheduled to take effect 30 days after the signing, but court challenges are expected. Opponents call it unconstitutional and note that six weeks is before many women know they’re pregnant.

Advanced technology can detect the first flutter of electric activity within cells in an embryo as early as six weeks. This flutter isn’t a beating heart; it’s cardiac activity that will eventually become a heart. An embryo is termed a fetus after the eighth week of pregnancy, and the actual heart begins to form between the ninth and 12th weeks of pregnancy.

The law allows the father, grandparents, siblings, aunts and uncles of a “preborn child” to each sue an abortion provider for a minimum of $20,000 in damages within four years after the abortion. Rapists can’t file a lawsuit under the law, but a rapist’s relatives could.

“The vigilante aspect of this bill is absurd,” said Idaho Democratic Rep. Lauren Necochea. “Its impacts are cruel, and it is blatantly unconstitutional.”

A Planned Parenthood official called the law unconstitutional and said the group was “committed to going to every length and exploring all our options to restore Idahoans’ right to abortion.”

“I want to emphasize to everyone in Idaho that our doors remain open. We remain committed to helping our patients access the health care they need, including abortion,” said Rebecca Gibron of Planned Parenthood Great Northwest, Hawaii, Alaska, Indiana and Kentucky, which operates Idaho’s three abortion clinics.

Backers have said the law is Idaho’s best opportunity to severely restrict abortions in the state after years of trying. Most recently, the state last year passed a six-week abortion ban law, but it required a favorable federal court ruling in a similar case to take effect, and that hasn’t happened.

The law is modeled after a Texas law that the U.S. Supreme Court has allowed to remain in place until a court challenge is decided on its merits. The Texas law allows people to enforce the law in place of state officials who normally would do so. The Texas law authorizes lawsuits against clinics, doctors and anyone who “aids or abets” an abortion that is not permitted by law.

A number of other states are pursuing similar laws, including Tennessee, which introduced a Texas-style abortion bill last week.

White House press secretary Jen Psaki said the Biden administration knew the Texas law would lead to other states passing similar laws, and called on Congress to send the president a bill to “shut down these radical steps.”

“This development is devastating for women in Idaho, as it will further impede women’s access to health care, especially those on low incomes and living in rural communities,” Psaki said in a statement Wednesday.

Republicans in Idaho have super-majorities in both the House and Senate. The measure passed the Senate 28-6 and the House 51-14 with no Democratic support. Three House Republicans voted against the measure.

Little on Wednesday noted his concerns with the legislation.

“Deputizing private citizens to levy hefty monetary fines on the exercise of a disfavored but judicially recognized constitutional right for the purpose of evading court review undermines our constitutional form of government and weakens our collective liberties,” he wrote.

He said that he worried some states might use the same approach to limit gun rights.

He also noted his concern with the part of the law allowing a rapist’s relatives to sue.

“Ultimately, this legislation risks retraumatizing victims by affording monetary incentives to wrongdoers and family members of rapists,” he wrote.

He concluded the letter by encouraging lawmakers to fix those problems to avoid unintended consequences “to ensure the state sufficiently protects the interests of victims of sexual assault.”

Little is facing a primary challenge from the far-right in McGeachin, the lieutenant governor, who has been endorsed by former President Donald Trump.

Republican Rep. Steven Harris, the bill’s sponsor, said in a statement after the vote on March 14, “This bill makes sure that the people of Idaho can stand up for our values and do everything in our power to prevent the wanton destruction of innocent human life.”