The US Supreme Court appears unlikely to agree with anti-abortion activists who want to overturn the federal government’s approval of a widely used abortion drug, a proposal that could have profound and far-reaching consequences for millions of Americans’ healthcare.

A majority of justices on the nine-member court on Tuesday were sceptical that a group of anti-abortion doctors have sufficient legal grounds to bring the case against the US Food and Drug Administration, which first approved the drug mifepristone in the year 2000.

But during Tuesday’s oral arguments in a case targeting the drug, at least two conservative justices floated the idea of dusting off a 151-year-old law that abortion rights advocates fear could be used to further strip access in the aftermath of the Supreme Court’s 2022 decision to revoke Americans’ constitutional right to abortion care.

The Comstock Act of 1873 targeted the mailing of contraceptives, pornography and any drug “intended for producing abortion, or for any indecent or immoral use.” It largely floundered under a series of congressional actions and the Supreme Court’s ruling in Roe v Wade 100 years later, but anti-abortion activists – as well as a federal judge who agreed to ban mifepristone, triggering the latest Supreme Court battle – have invoked the law following a decades-long anti-abortion crusade from conservative Christian legal groups.

A case before the Supreme Court argues that the FDA wrongfully approved mifepristone for use up to 10 weeks of pregnancy, and then improperly eliminated requirements that the drug should only be dispensed in person.

On Tuesday, Supreme Court Justice Samuel Alito – who wrote the 2022 decision to overturn Roe v Wade – suggested that the FDA should have “considered” Comstock.

Justice Clarence Thomas later suggested that the manufacturer of the mifepristone drug Mifeprex may have “a Comstock problem.” He said it “specifically covers drugs such as yours.”