"Evidence that children raised in this particular environment may someday have their physical health and safety threatened is not evidence that the danger is imminent enough to warrant invoking the extreme measure of immediate removal," the court wrote.
Texas officials took all the sect's children into custody last month, claiming the group encourages marriage between underage girls and older men, placing the children at risk of abuse, which members of the Fundamentalist Church of Jesus Christ of Latter Day Saints deny.
At a two-day group hearing last month, Walther ordered that all the children be kept in temporary state custody. Walther has 10 days to comply with today's ruling.
The state had said that as many as 31 sect girls in state custody were underage and either pregnant or already had children. But at a series of follow-up hearings that began this week, the state has admitted that 15 of those girls are older than 18.