Idaho became the first state to comply with Texas and passed the law banning abortion after six weeks.
The law will enter into force in a month, but before that court proceedings are expected.
Opponents of the law say that the law is unconstitutional and that few women even know they are pregnant before week six.
The law also means that doctors who perform an abortion after cardiac activity is detected on an embryo can be sued, something that Republican Gov. Brad Little signed - but also expressed concern about whether the law was constitutional and whether the introduction was really wise.
The law allows the father, grandparents, siblings, aunts and uncles of a fetus to sue the performer of the $ 20,000 abortion within four years of the abortion.
Rapists can not file a lawsuit according to the law, but relatives of a rapist.
- The vigilante aspect of this bill is absurd.
Its effects are cruel and it is clearly unconstitutional, said Idaho's Democratic Representative Lauren Necochea.
"Our doors remain open"
The organization Planned Parenthood, which includes counseling and activities in sex and cohabitation and abortion, called the law unconstitutional and said it will "explore all of our options for restoring Idaho residents' 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, says Rebecca Gibron of Planned Parenthood, who runs one of Idaho's three abortion clinics.
The law was passed in Texas in September, leading to widespread protests - both for and against.
President Joe Biden, who believes the law is unconstitutional, began a process to stop it, resulting in a federal judge temporarily halting the law in October.
But just two days later, the Court of Appeal decided to reintroduce the ban.