The Trump administration said it would start revoking the passports of Americans who owe more than $2,500 in child support payments, seeking to enforce a decades-old federal law.

President Bill Clinton signed the Personal Responsibility and Work Opportunity Act in 1996, a law that enacted significant changes to the federal social safety net. Among those changes was a provision that the State Department be notified of people with delinquent child support debts. It said that the secretary of state “may revoke, restrict, or limit a passport issued previously to such individual.”

In a statement, the State Department said that the agency “is using common sense tools to support American families and strengthen compliance with U.S. laws,” adding that revoking passports “supports the welfare of American children by exacting real consequences for child support delinquency under existing federal law.”

It is unclear how many citizens could have their passports revoked under the policy, or when enforcement would start. The State Department did not immediately respond to a request for comment.

The Clinton-era law has not been strictly enforced in the past, and enforcement has usually been focused on blocking those with child support debt from renewing or applying for a new passport.

In the 1998 case of Eudene Eunique, for example, Ms. Eunique was denied a passport after the Department of Health and Human Services reported to the State Department that she owed more than $20,000 in child support payments to her ex-husband. Ms. Eunique sued in federal court, arguing that the law violated her Fifth Amendment right to travel. The Ninth Circuit Court of Appeals ultimately ruled against her and upheld the law in 2002.

The State Department has estimated that the passport rule has led to the collection of more than $382 million in child support payments since its inception. The agency also reported that it was tracking 4.3 million people with outstanding child support debt, and that nearly 100 passport applications are denied every day over child support.

There have been several legislative efforts to tighten enforcement of the passport rule. A 2005 law lowered the threshold for enforcement from $5,000 in unpaid child support to $2,500. Another bill in 2007 sought to make the passport revocation mandatory, rather than at the discretion of the State Department, but that never passed.