HOUSTON — Texas authorities had no right to take more than 400 children from a secluded polygamist compound last month because officials never proved that the children were in imminent danger, a state appeals court ruled yesterday.

The ruling by the Third Court of Appeals in Austin did not specifically call for the state to return children to their mothers. But it laid waste to the state’s arguments for taking all the children, opening the door for at least some of the polygamist families to be reunited within weeks.

It was triggered by a lawsuit by Texas RioGrande Legal Aid, a group that represents 38 mothers in the ongoing child custody battle, one of the largest in U.S. history.

“The way that the courts have ignored the legal rights of these mothers is ridiculous,” an attorney for the legal aid group, in a statement, Julie Balovich, said. “It was about time a court stood up and said that what has been happening to these families is wrong.”

The decision was another setback for Texas officials, who in recent days have conceded that at least 15 of the young mothers the state had initially detained as child brides are in fact adults. One turned out to be 27 years old.

Texas officials have maintained that they were legally compelled to remove all the children from the Yearning for Zion Ranch because their investigation uncovered widespread evidence of children being sexually abused and of teenage girls, some visibly pregnant, who were in polygamous marriages with older men.

But members of the Fundamentalist Church of Jesus Christ of Latter-day Saints, a 10,000-member sect that split from the mainstream Mormon Church after it banned polygamy in 1890, have strongly denied state claims that all children were in danger of abuse in the compound’s communal dormitories.

The appeals court sided with the sect, ruling that the Texas Department of Family and Protective Services erroneously treated the entire 1,691-acre YFZ Ranch in West Texas as an individual household. It concluded that even if state officials could prove abuse was occurring in some families, it did not mean all children were at risk. It also noted that state officials presented no evidence showing that boys and prepubescent girls were in peril.

“Even if one views the FLDS belief system as creating a danger of sexual abuse by grooming boys to be perpetrators of sexual abuse and raising girls to be victims of sexual abuse as the Department contends, there is no evidence that this danger is ‘immediate’ or ‘urgent,'” the ruling stated.

The ruling gave a trial court in San Angelo 10 days to vacate orders granting Texas temporary custody of more than 400 children, which allowed the state to send the children to foster care homes until their future was determined. At one point Texas stated it had 468 children in custody, but some have proven to be adults.

Though the case was not filed on behalf of all parents or children, attorneys said they were optimistic that the ruling had established a foundation for all the children to be returned to their parents soon.

“My head is still spinning,” a Dallas appellate lawyer who represents a 2-year-old girl, Susan Hays, said. “Removing a child from home should be the last option, not the first. I’m so happy we still have the rule of law in Texas.”