If allowed to remain in force, the law would be the most far-reaching restriction on abortion rights in the United States since the high court's landmark Roe v. Wade decision legalized abortion across the country in 1973.
The Texas law, signed by Republican Gov. Greg Abbott in May, prohibits abortions once a heartbeat can be detected in a fetus, usually around six weeks and before most women know they're pregnant.
In a statement after the law took effect, President Joe Biden said it "blatantly violates the constitutional right established under Roe v. Wade and upheld as precedent for nearly half a century."
The president later added on Twitter, "Texas SB8 will impair women's access to health care and, outrageously, deputizes private citizens to sue those they believe helped another person get a banned abortion ... We will protect and defend that right."
Texas SB8 will impair women's access to health care and, outrageously, deputizes private citizens to sue those they believe helped another person get a banned abortion.— President Biden (@POTUS) September 1, 2021
It's a blatant violation of the right established under Roe V. Wade. We will protect and defend that right.
In a phone call with reporters early Wednesday, Marc Hearron, a lawyer for the Center for Reproductive Rights, said that "as of now, most abortion is banned in Texas." Hearron said the abortion providers his group represents were still hoping to hear from the Supreme Court.
They have said the law would rule out 85% of abortions in Texas and force many clinics to close. Planned Parenthood is among the abortion providers that have stopped scheduling abortions beyond six weeks from conception.
Abortion rights advocates say the Texas law will force many women to travel out of state for abortions, if they can afford to do so and also navigate issues including childcare and taking time off work. It is also expected to increase the number of women seeking to self-induce abortions using pills obtained by mail.
At least 12 other states have enacted bans on abortion early in pregnancy, but all have been blocked from going into effect.
What makes the Texas law different is its unusual enforcement scheme. Rather than have officials responsible for enforcing the law, private citizens are authorized to sue abortion providers and anyone involved in facilitating abortions. Among other situations, that would include anyone who drives a woman to a clinic to get an abortion. Under the law, anyone who successfully sues another person would be entitled to at least $10,000.
SEE MORE: Texas can ban common abortion procedure in 2nd trimester, appeals court rules
Abortion opponents who wrote the law also made it difficult to challenge the law in court, in part because it's hard to know whom to sue.
Late into the night Tuesday before the ban took effect clinics were filled with patients, said Amy Hagstrom Miller, CEO of Whole Women's Health, which has four abortion clinics in Texas.
Twenty-seven women were still in the waiting room after 10 p.m. at one clinic, leaving doctors crying and scrambling over whether they would see all of them in time, she said. The last abortion at one of her clinics finished at 11:56 p.m. in Fort Worth, where Hagstrom Miller said anti-abortion activists outside shined bright lights in the parking lot after dark looking for wrongdoing, and twice called police.
"This morning I woke up feeling deep sadness. I'm worried. I'm numb," she said.
On the other side, Republican state Rep. Shelby Slawson wrote on Facebook after the ban took effect that it was "with great sadness that I relate to you that late into the night, some in Texas were scrambling to end as many unborn lives as they could before the clock struck midnight." Her colleague, Republican state Rep. Jeff Leach wrote on Twitter after the ban went into effect that "LIFE is winning in America ... and Texas is leading the way!"
The law is part of a hard-right agenda that Texas Republicans muscled through the statehouse this year ahead of the 2022 midterm elections, when Abbott is up for a third term as governor.
Another law taking effect Wednesday ended required firearm training and background checks to carry handguns in public in Texas, and GOP lawmakers on Tuesday approved election changes that will further tighten what are already some of the strictest voting laws in the nation.
Texas has long had some of the nation's toughest abortion restrictions, including a sweeping law passed in 2013. The Supreme Court eventually struck down that law, but not before more than half of the state's 40-plus clinics closed.
Lawmakers also are moving forward in an ongoing special session in Texas with proposed new restrictions on medication abortion, a method using pills that accounts for roughly 40% of abortions in the U.S.
Even before the Texas case arrived at the high court the justices had planned to tackle the issue of abortion rights in a major case that will be heard after the court begins hearing arguments again in the fall. That case involves the state of Mississippi, which is asking to be allowed to enforce an abortion ban after 15 weeks of pregnancy.