The core of the PKPA is its requirement that one State may not modify a child custody determination made by the court of another State unless (1) the State seeking to modify has jurisdiction to make such a child custody determination and (2) the court of the other State no longer has jurisdiction or has declined to exercise jurisdiction. The key distinction between the PKPA and the Uniform Child Custody Jurisdiction Act (UCCJA) is that under the UCCJA any one of the two conditions set in the PKPA is sufficient to confer jurisdiction upon a State court, thus creating the possibility of concurrent jurisdiction between two States. The PKPA, on the other hand, eliminates the possibility of concurrent jurisdiction by conferring exclusive modification jurisdiction upon the State which rendered the initial decree. Various court decisions involving the interpretation of PKPA have validated its intent. For example, in Pierce v. Pierce, the Montana Supreme Court ruled that the State considering modification of another State's custody decree must apply the law of the State rendering the initial decree in determining whether jurisdiction existed in the decree State. In Flood v. Braaten, the U.S. Third Circuit Court of Appeals ruled that Federal courts are a proper forum for resolving the impasse created by competing decrees of two States. The major weakness in PKPA involves enforecement barriers which typically characterize the Federal system due to shortages of money and manpower. The Federal Parental Locator Service, designed to locate and apprehend parental abductors who flee across State lines, has not been as effective as hoped. Sixty-seven footnotes are provided.