Opponents of a Georgia law banning abortions once a fetal heartbeat can be detected vow to take their fight from the state Capitol to the courthouse.

Signed Tuesday by Republican Gov. Brian Kemp, the measure is one of the nation’s most restrictive abortion laws and would effectively ban the procedure around six weeks of pregnancy, before many women know they are pregnant.

Staci Fox, the president and CEO of Planned Parenthood Southeast, said at a news conference that she had one message for Kemp: “We will see you, sir, in court.”

The organization also planned to campaign to unseat lawmakers who supported it, saying they would “be held accountable for playing politics with women’s health.”

The legal director of the ACLU of Georgia, Sean Young, has said the measure is unconstitutional, and the group plans to challenge it in court.

“Under 50 years of Supreme Court precedent, this abortion ban is clearly unconstitutional,” Young said in a recent interview with The Associated Press. “Every federal court that has heard a challenge to a similar ban has ruled that it’s unconstitutional.”

Kemp said he approved the bill “to ensure that all Georgians have the opportunity to live, grow, learn and prosper in our great state.”

The signing caps weeks of tension and protests at the state Capitol and begins what could be a lengthy and costly legal battle. “We will not back down,” Kemp said, acknowledging the likelihood of a legal challenge. “We will always continue to fight for life.”

Anti-abortion activists and lawmakers across the country have been energized by the new conservative majority on the U.S. Supreme Court that includes President Donald Trump appointees Neil Gorsuch and Brett Kavanaugh. They are pushing abortion bans in an attack on the high court’s 1973 Roe v. Wade ruling, which legalized abortion nationwide until a fetus is developed enough to live outside a woman’s uterus.