COLUMBIA, S.C. - The South Carolina Supreme Court sharply limited the ability of Family Court judges to order visitation rights for grandparents in a ruling Monday.

Susan and Terry Smith appealed a lower court ruling. The couple said the judge unconstitutionally required visits between their three children and her parents, Benjamin and Bethanne Camburn of Conway.

Showing "a child may benefit from contact with the grandparent, or that the parent's refusal is simply not reasonable in the court's view, does not justify government interference in the parental decision," the unanimous high court said in overturning a Family Court decision.

Before Monday's ruling, grandparents in South Carolina could petition for visitation with their minor grandchildren if the parents of the children were separated or divorced. The grandparents had to show that the visits would be in the best interest of the children and that they had an existing relationship with their grandchildren.

The grandparents had to show that visits would not interfere with the parent-child relationship.

Now, however, grandparents would have to show other factors, such as "significant harm" if visitation wasn't allowed, the court said.

"That's going to be a really tough one for grandparents to meet," said Rochelle Bobroff, a lawyer for AARP.

Before 1965, grandparents had no rights under the law to visit their grandchildren, the AARP says. Legislatures changed that and every state has some form of grandparent visitation rights law.

But those laws are under greater scrutiny since a 2001 U.S. Supreme Court decision that overturned broad child visitation rights for grandparents and others.

With that decision, a court has to "allow a presumption that a fit parent's decision is in the child's best interest," the state Supreme Court said. The Family Court's ruling granting visitation "unduly interfered" with the parents' rights in the "care, custody and control of their own children," the high court said.

The South Carolina decision is similar to state supreme court opinions in Georgia, Iowa, Michigan, Tennessee and Washington that have said courts can require grandparents show a child would be harmed without their visits. But other cases have used a standard of what's in the child's best interest, including a recent case in Massachusetts, Bobroff said.

South Carolina's case was different in one regard, Bobroff said.

"In all of the cases that I've ever seen, there really isn't an allegation that the parents are unfit," Bobroff said.

The lower court noted that while the Smiths were separated, she took her children to Maryland, where the biological father of one of the children fled to avoid arrest; she kept the children out of school during that time and her parents had her involuntarily committed to a psychiatric care when she returned.

"There is no clear and convincing evidence here that mother or husband is unfit, nor did the Family Court make any such finding," the state Supreme Court said.