"Today’s decision ensures that the women of Arkansas will remain protected from this blatant unconstitutional assault on their health and fundamental reproductive rights," said CRR President and CEO Nancy Northup.
Arkansas's GOP legislature passed the so-called "heartbeat" ban, one of the nation's most stringent abortion policies, in March.
It prohibits abortion after a fetal heartbeat can be detected by abdominal ultrasound. Exceptions exist for cases of rape, incest, a threat to the woman's life and certain fetal disorders.
The ban is seen as a challenge to Roe v. Wade along with its even stricter counterpart in North Dakota, where abortion is prohibited after as few as six weeks of gestation.