The law goes into effect immediately.
MS only has one medical facility that performs abortions in the state, Jackson Women's Health, and the clinic has vowed to fight the new law. Bryant calls Reeves' ruling "disappointing".
The new law bans most abortions after 15 weeks of pregnancy, down from the state's previous 20 weeks.
In papers filed earlier Monday evening, the Jackson Women's Health Organization and a physician who practices there stated that a woman who is 15 weeks or more pregnant is scheduled to have an abortion Tuesday afternoon.
"Accordingly, the ban is unconstitutional as applied to all women seeking pre-viability abortions after 15 weeks". The suit was filed in the U.S. District Court for the Southern District of MS and listed both the Jackson Women's Health Organization and the abortion provider's resident physician, Dr. Sacheen Carr-Ellis, as plaintiffs.
Republican Gov. Phil Bryant signed House Bill 1510 on Monday afternoon.
Carr-Ellis, in a sworn statement, says she'll have to stop providing abortions to women past the 15 week ban, or else lose her MS medical license, as House Bill 1510 requires. Current federal law blocks such restrictions by states.
Reeves said in his order that the MS law "places viability at 15 weeks - about two months earlier than where the medical consensus places it".
The cases Reeves cited-Roe, Casey, and Hellerstedt-all prohibit a state from interfering with a pregnant person's right to a pre-viability abortion.
"We'll probably be sued in about half an hour", Bryant said to laughter from supporters as he signed the bill.
Three clinics in Louisiana perform abortions and the process to access the procedure has been heavily regulated by state lawmakers. Later on Monday, the organisation filed a motion for a temporary restraining order, said Robert B. McDuff, one of the lawyers for the clinic.
Paul Barnes, a special assistant to the attorney general, said that as gestational age increases so does the risk to women.
Reeves did not rule from the bench but said he would rule as soon as possible. She was at 15 weeks or more of gestation which, according to the Associated Press, exceeded the time frame during which Mississippi's new law permitted certain abortions. He says MS is "saving more of the unborn than any state in America".
According to the research, only just over half of women in poor and under-developed countries have access to pregnancy-related medical services, while two thirds having such access in lower-middle income countries and almost 95 percent access in upper-middle income states. In fact, the only exceptions to law are if the fetus has an issue that is "incompatible with life" or if the mother's life or "major bodily function" would be threatened by carrying the pregnancy to full term. There are no exceptions for incidents of rape or incest.