Glenn Pappas (plaintiff) and Nan O’Brien (defendant) were divorced in California after six years of marriage and the birth of two sons, A.P. and P.P. The California court order awarded Pappas and O’Brien joint legal custody of the two sons, with O’Brien having primary physical custody and Pappas paying child support. Pappas moved to Oklahoma, while O’Brien and the children moved to Georgia, where O’Brien registered the California divorce and custody decree. Thereafter, O’Brien filed a petition in Georgia against Pappas to increase child support. The Georgia court granted O’Brien’s petition and explicitly stated that Pappas’s child-support requirement would cease if custody was later changed by a court of competent jurisdiction. Two years later, P.P. moved in with Pappas in Oklahoma. Pappas filed a petition in Oklahoma to gain physical custody of P.P. and to stop child-support payments for A.P., who had reached the age of majority. After a hearing, the Oklahoma court awarded custody of P.P. to Pappas and retroactively relieved Pappas of any child-support obligation. Additionally, the court ordered O’Brien to pay retroactive and ongoing child support to Pappas for the benefit of P.P. Later, P.P. returned to live with O’Brien in Georgia, and Pappas sought enforcement of child support for the time when P.P. was in his custody. An administrative law judge issued an order awarding Pappas retroactive child support. O’Brien then moved to Vermont. Pappas, through Vermont’s Office of Child Support (OCS) (plaintiff), filed a petition to register the Oklahoma support order pursuant to the Uniform Interstate Family Support Act (UIFSA). O’Brien filed a motion to set aside the support order. The Vermont court registered the Oklahoma order, and O’Brien appealed. The court of appeals affirmed. O’Brien filed documents to stay the Vermont court’s order and register the Georgia child-support order. OCS filed a motion to dismiss O’Brien’s action. The Vermont court granted OCS’s motion, and O’Brien appealed. The Supreme Court of Vermont consolidated the two appeals for review.