The United States Postal Service can deliver prescribed abortion medication, even in states where abortion access is severely restricted, the Department of Justice announced.
The department's Office of the Legal Counsel wrote in an opinion that pills being sent through the mail is not in violation of the Comstock Act -- an 1873 law that made it illegal to send "obscene" material in the mail -- if the sender does not know if the drugs will be used illegally.
It comes on the heels of the U.S. Food and Drug Administration giving pharmacies the green light to fill prescriptions for one of the pills, mifepristone, if a certified health care provider prescribes the drug and if that pharmacy meets certain requirements.
The Comstock Act, which was passed by Congress under the administration of Ulysses S. Grant, criminalized the act of using the U.S. Postal Service to send contraceptives, substances that induce abortion, pornographic content, sex toys and any written material about these items.
The Postal Service had requested the opinion from the office after the Supreme Court overturned Roe v. Wade in June 2022 and states began enforcing their own bans.
"We conclude that [the act] does not prohibit the mailing, or the delivery or receipt by mail, of mifepristone or misoprostol where the sender lacks the intent that the recipient of the drugs will use them unlawfully," Christopher Schroder, assistant attorney general for the OLC, wrote in the opinion.
"Because there are manifold ways in which recipients in every state may lawfully use such drugs, including to produce an abortion, the mere mailing of such drugs to a particular jurisdiction is an insufficient basis for concluding that the sender intends them to be used unlawfully," the opinion continued.
In a statement to ABC News, USPS said the opinion "confirms that the Comstock Act does not require the Postal Service to change our current practice, which has been to consider packages containing mifepristone and misoprostol to be mailable under federal law in the same manner as other prescription drugs."
Drugs for medication abortions were first developed in the late 1970s as an alternative, non-surgical, form of abortion in which someone takes two pills to end a pregnancy.
The first pill is mifepristone, which was authorized by the U.S. Food and Drug Administration in 2000. It works by blocking the hormone progesterone, which the body needs to continue a pregnancy.
This causes the uterine lining to stop thickening and to break down, detaching the embryo. The second drug, misoprostol, taken 24 to 48 hours later, causes the uterus to contract and dilates the cervix, which will expel the embryo.
In the U.S., the drugs are approved up to 10 weeks' gestation, although the World Health Organization says they can be taken up until the 12-week mark.
As of 2020, medical abortions account for 54% of abortions performed in the U.S., up from 24% a decade ago, according to the Guttmacher Institute.
In December 2021, the FDA permanently lifted its restrictions on abortion pills, allowing them to be sent by mail than requiring them to be given in person.
ABC News' Anne Flaherty contributed to this report.