JACKSON, Miss. — Mississippi lawmakers Thursday passed what would be the nation’s most restrictive abortion law, making the procedure illegal in most cases after 15 weeks of pregnancy. The state’s only abortion provider pledged to sue, and the attorney general said he expected a tough legal battle ahead.

Lawmakers in the Republican-controlled Legislature appeared to not only expect, but to encourage, such challenges in hopes the issue will eventually make its way to the U.S. Supreme Court.

The House voted 75-34 in favor of the bill , and Republican Gov. Phil Bryant said again Thursday that he would sign it. Because of necessary paperwork, it won’t reach his desk until next week. The Senate passed the measure Tuesday.

“We are protecting more women, we are protecting more children,” said House Judiciary B Committee Chairman Andy Gipson, a Braxton Republican. “By 15 weeks, you have a child in the womb who has a heartbeat, who for all practical purposes has taken on the form of a person.”

Under the Supreme Court’s 1973 Roe v. Wade ruling establishing a nationwide right to abortion, states were permitted to restrict abortions after viability – the point when the fetus has a reasonable chance of surviving under normal conditions outside the uterus. The ruling offered no legal definition of viability, saying it could range between 24 and 28 weeks into a pregnancy.

The Mississippi measure “seems like a pretty simple bill designed to test the viability line that the Supreme Court has drawn,” said David Forte, a law professor at Ohio’s Cleveland State University.

Abortion-rights-groups immediately spoke out against the bill, saying it is not legally or medically sound.

“We certainly think this bill is unconstitutional,” said Katherine Klein, equality advocacy coordinator for the American Civil Liberties Union of Mississippi. “The 15-week marker has no bearing in science. It’s just completely unfounded and a court has never upheld anything under the 20-week viability marker. … We expect that this bill will be challenged in court and it will lose and, in the process, Mississippi will lose thousands upon thousands of taxpayer dollars.”

Anti-abortion groups applauded the measure.

“We’re thrilled that Mississippi lawmakers are taking a step to protect the basic right to life, as well as protecting maternal health,” said Jameson Taylor, acting president of the conservative-leaning Mississippi Center for Public Policy. The center helped craft the bill.