Justice Samuel Alito said the plaintiffs argued in court filings that studies have shown after the 2021 change from the FDA that allowed mifepristone to be mailed that there was an increase in emergency room visits.

He asked Solicitor General Elizabeth Prelogar if the FDA's response -- that there were not increases in side effects from the drug -- was proper.

Preolgar said this was a reasoned explanation from the FDA and the agency acknowledged that while some studies have shown the availability of abortion pills by mail led to more ER visits, this did not equate to "more serious adverse effects."

"Many might go because they are experiencing heavy bleeding which mimics a miscarriage and they need to know whether or not they are having a complication," she said.

Being cited in the arguments is the Comstock Act, a 151-year-old law under which it's illegal to use carriers such as the United States Postal Service to mail "obscene" materials such as drugs that induce abortions.

The Alliance for Hippocratic Medicine has said the FDA's decision to allow patients to receive mifepristone by mail instead of in person from certified health providers specifically violates the Comstock Act.

Solicitor General Elizabeth Prelogar, pressed by Justice Samuel Alito on why the FDA didn't consider the application of the Comstock provisions, said she did not think it fell under the FDA's "lane."

"And we don't think it means what respondents suggested," Prelogar said of the law.

Read more about the Comstock Act here.

Amid questions from the Supreme Court about who has standing to sue, Solicitor General Elizabeth Prelogar said the federal government believes individual doctors still have broad "conscience protections" if they oppose abortion and decline to provide such access in specific instances.

Prelogar reaffirmed that later in the hearing when some justices returned to the topic but noted that the government believes there are exceptions under the law.

Preolgar previously argued that the government does not believe states have standing in this case to sue.

Solicitor General Elizabeth Prelogar is arguing the supposed harm cited by the anti-abortion alliance is "unduly speculative" and hypothetical.

"Their theories rest on a long chain of remote contingencies," she said. "Only an exceptionally small number of women suffer the kind of serious complications that could trigger any need for emergency treatment. It's speculative that any of those woman would seek care from the two specific doctors who asserted conscience injuries."

Prelogar also asserted that if there were any safety consequences to a drug, the FDA could take action itself to fix it.

The lead plaintiff, the Alliance for Hippocratic Medicine, had initially challenged the FDA’s approval of mifepristone.

But the matter before the high court now is more narrow -- whether the FDA's subsequent regulatory decisions about the drug, in 2016 and 2021, were sound.

In court filings, the Alliance Defending Freedom, a Christian conservative legal advocacy representing the plaintiffs, has claimed mifepristone is not safe and that the FDA didn't study it closely enough before it was approved.

The group also argued that the FDA’s decisions in 2016, lowering the recommended dosage and extending the use from seven weeks through 10 weeks of pregnancy, and in 2021, which permanently lifted the restriction on requiring abortion pills to be dispensed in-person, were unsound.

In January 2022, the FDA went further by allowing retail pharmacies to provide the drug too, either by mail or in person, so long as they meet certain requirements, which the plaintiffs claim violate federal laws that prohibit the distribution of chemical abortion drugs by mail.

The FDA rejects the claims, arguing that mifepristone is safe when used as indicated and directed, and that the pill went through a thorough and comprehensive review before being approved.