A legal loophole in Idaho that allows parents of teens to nullify child custody agreements by arranging child marriages will remain in effect, under a ruling from the state Supreme Court on Tuesday.

In a split decision, the high court declined to decide whether Idaho’s child marriage law — which allows 16- and 17-year-olds to marry if one parent agrees to the union — is unconstitutional. Instead, the justices said that once a child is emancipated by marriage, the family court loses jurisdiction over custody matters.

The case arose from a custody battle between a Boise woman and her ex-husband, who planned to move to Florida and wanted to take their 16-year-old daughter along. The ex-husband was accused of setting up a “sham marriage” between his daughter and another teen as a way to end the custody fight.

It’s not a rare scenario — all but seven states allow minors below the age of 18 to marry, according to Unchained At Last, an organization that opposes child marriage. Nevada, Idaho, Arkansas and Kentucky have the highest rates of child marriage per capita, according to the organization. Although minors are generally considered legally emancipated once they are married, they generally still have limited legal rights and so may be unable to file for divorce or seek a protective order.

Erin Carver and William Hornish divorced in 2012, and only their youngest was still living at home last year when both sides began disputing the custody arrangements.

Carver said she learned Hornish was planning a “sham marriage” for the teen to end the custody battle, and asked the family court magistrate to stop the marriage plans. Several days later, the magistrate judge agreed, but it was too late. The teen had already married.

The high court heard arguments in March, and Carver’s attorney contended that the child marriage law is unconstitutional because it allows one parent to terminate another parent’s rights without due process. Hornish’s attorney, Geoffrey Goss, countered that his client had acted legally and followed state law.

In Tuesday’s ruling, a majority of the Supreme Court justices said that because the marriage had occurred before an initial ruling was made, the family court lost jurisdiction. Once a child is married, they are emancipated and no longer subject to child custody arrangements, the high court said.