OPINION OF THE COURT
ROBERTS, Justice.This is an appeal from an order of the Superior Court reversing a custody decree of the Court of Common Pleas of Greene County. The court of common pleas determined that a Danish custody decree in favor of appellee, Marianne Hoemje, should be modified and custody awarded instead to appellant, Thomas Zaubi. The Superior Court, however, unanimously determined that, in modifying the Danish decree, the court of common pleas had incorrectly applied the Uniform Child Custody Jurisdiction Act, P.L. 29, §§ 1 et seq., 11 P.S. §§ 2301 et seq., effective July 1, 1977 (hereinafter “Act”). We agree with the Superior Court that the Act compels Pennsylvania courts not only to recognize valid custody decrees from foreign nations but also to decline to accept jurisdiction to modify custody decrees in the absence *186of a showing, based on evidence not previously considered, of conditions in the custodial household that are physically or emotionally harmful to the children. Because appellant failed to make such a showing, we affirm the order of the Superior Court.
The facts of this case are more fully set forth in the opinion of the Superior Court at 275 Pa.Super. 294, 418 A.2d 729 (1980). In essence, however, appellee Marianne Hoejme, a Danish citizen, was granted custody of her children in Denmark after numerous hearings and an appeal by her husband, appellant Thomas Zaubi, to the High Court of Denmark. At all of these proceedings, appellant was present and represented by counsel. On June 16, 1977, appellee received a final divorce decree. At this time appellant was able to appeal his case once more to the High Court of Denmark, and a hearing was scheduled for November 17, 1977. In August 1977, while the children were in his care during a visitation period, and while his custody appeal was pending, appellant fled with the children to the United States.1
Upon returning to the United States, appellant concealed the whereabouts of the children from their mother for over eight months by shuttling them between Cleveland and Nemacolin. At no time during this period were they enrolled in school. When appellee finally located the children in May 1978, she filed a Petition for a Writ of Habeas Corpus in the Court of Common Pleas of Greene County to obtain enforcement of the Danish custody decree. Service was effected on the Zaubi family in Nemacolin, but appellant again fled with the children to avoid the court’s jurisdiction, returning only after the court had issued a contempt citation against his parents.
I
Among the purposes for which our Legislature enacted the Uniform Child Custody Jurisdiction Act of 1977 is the *187deterrence of “abductions and other unilateral removals of children undertaken to obtain custody awards.” 11 P.S. § 2302(a)(5).
Section 9(b), 11 P.S. § 2309(b), provides that
“(b) Unless required in the interest of the child, the court shall not exercise its jurisdiction to modify a custody decree of another state if the petitioner, without consent of the person entitled to custody, has improperly removed the child from the physical custody of the person entitled to custody or has improperly retained the child after a visit or other temporary relinquishment of physical custody. If the petitioner has violated any other provision of a custody decree of another state the court may decline to exercise its jurisdiction unless the petitioner can show that conditions in the custodial household are physically or emotionally harmful to the child, the burden of proof being on the petitioner requesting the court to take jurisdiction.”
As used in the above section, “petitioner” clearly refers to the party seeking modification of the custody decree.2 It does not refer, as the dissenting opinion would have it, to an “innocent” party who, as here, is merely seeking the enforcement of a valid custody decree rendered in another jurisdiction and who happens to have been the first to petition the court to act.
Since section 9(b) undoubtedly applies to the Greene County proceedings, the next question is what showing the petitioner for modification must make under that section in order for the Greene County court to be permitted to exercise its jurisdiction to modify the valid Danish decree. On the one hand, in cases where the petitioner has improperly abducted the children, a court “shall not exercise its jurisdiction to modify” “[ujnless required in the interest of the child” (that is, in the words of the commissioner’s note, *188“unless the harm done to the child by a denial of jurisdiction outweighs the parental misconduct”). On the other hand, in cases of less flagrant violations of custody decrees, a court “may decline to exercise its jurisdiction unless the petitioner can show that conditions in the custodial household are physically or emotionally harmful to the child. ...”3 We cannot conclude from this language that the Act places a lesser burden on a petitioner who, as here, has abducted his children than on one who has simply violated some other provision of a custody decree. Such a conclusion defies not only the stated purposes of the Act but common sense as well. It is inconceivable that in replacing the vague language of the Uniform Act with a more definite and rigorous standard, our Legislature intended to make it easier for a parent who abducts his children to obtain the modification of a custody decree than for a parent who otherwise violates a valid decree. Thus, the courts below were correct in their determination that a showing of “physically or emotionally harmful” conditions in the custodial household was a necessary prerequisite to the exercise by the Greene County court of its jurisdiction to modify the Danish decree.
II
Two questions remain: (1) what evidence could the Greene County court properly consider in determining whether harmful conditions existed; and (2) in light of this evidence, has appellant met his burden of proof? The Greene County court. held that appellant had shown the existence of conditions sufficiently harmful to require a change of custody. However, the court based its decision almost entirely upon factual issues which had previously been litigated and resolved against appellant in the Danish courts.4 As the Superior Court correctly observed, the *189Greene County court erred in failing to defer to the findings of those courts.
Section 13 of the Act provides that “a custody decree rendered by a court of this State . .. binds all parties .. . who have submitted to the jurisdiction of the court, and who have been given an opportunity to be heard. As to these parties, the custody decree is conclusive as to all issues of law and fact decided and as to the custody determination made unless and until that determination is modified pursuant to law, including the provisions of this act.” 11 P.S. § 2313. Such conclusiveness was obviously intended to extend to custody decrees of other states as well, for it would be unthinkable for the Legislature, in adopting a uniform act, to pronounce the decrees of its own courts res judicata while denying similar effect to the decrees of sister states.
Appellant had proper notice and opportunity to be heard; indeed, a hearing date had been scheduled for his second appeal to the High Court of Denmark at the time appellant fled to the United States with his children. To say, as the dissenting opinion does, that in this situation a Pennsylvania court “may even exercise its independent judgment on the same facts that determined the foreign state’s order, “Irizarry Appeal, 195 Pa.Super. 104, 108, 169 A.2d 307, 309, cert. denied, 368 U.S. 928, 82 S.Ct. 363, 7 L.Ed.2d 191 (1961), is to ignore the intent of the Legislature in adopting the Act in 1977 and to issue an open invitation from the courts of Pennsylvania to those who, like appellant, would take the law into their own hands.5
*190Because section 13 of the Act makes conclusive all issues determined by the valid Danish decree, in the proceedings before the Greene County court appellant had the burden of proving by evidence not previously considered that conditions in appellee’s household were “physically or emotionally harmful to the child[ren].” Appellant did not meet that burden. Instead he evaded the jurisdiction of the Danish court, flouted its decree, and relitigated in a “friendlier” forum the very issues which the Danish court had decided against him. Such a result is precisely what the 1977 Uniform Child Custody Jurisdiction Act is intended to prevent. The sound analysis of the Superior Court fully reflects our Legislature’s intent in adopting the Uniform Act.
The unanimous order of the Superior Court is therefore affirmed.
LARSEN, J., joined the Opinion of the Court and filed a concurring opinion. NIX, J., filed a dissenting opinion in which FLAHERTY and KAUFFMAN, JJ., joined.. As a result of his actions, the Danish authorities have charged appellant with kidnapping. A warrant for his arrest awaits him if he should attempt to return to Denmark.
. See Uniform Child Custody Jurisdiction Act (U.L.A.) § 8, Commissioner’s Note and cases cited; e. g., Leathers v. Leathers, 162 Cal.App.2d 768, 328 P.2d 853 (1958) (courts will usually enforce decrees of sister states by invoking “clean hands” doctrine when there has been misconduct by the “parent seeking reexamination”).
. Our Legislature substituted the above language when it adopted the Act. In the Uniform Act this phrase reads “may decline to exercise jurisdiction if this is just and proper under the circumstances.”
. The court also expressed concern that if appellee returned to Denmark with her children after enforcement of the Danish decree, appellant would be unable to visit them because of the outstanding *189warrant for his arrest in that country. See note 1, supra. It was clearly inappropriate for the court to consider this factor in appellant’s favor in making its determination.
. The dissenting opinion observes that to interpret § 15(b) of the Act (courts shall give “due consideration” to record of previous proceedings) as “usurping the hearing court’s right to exercise its independent judgment on the same facts that determined the foreign order ... would require a jurisdiction to give greater deference to a foreign award than would be allowed under its laws to its own pronouncements in this area.” It should be noted, however, that in adopting *190section 13 of the Commonwealth Child Custody Jurisdiction Act, P.L. 108, § 13, 11 P.S. § 2413, effective June 27, 1978 (a provision exactly similar to section 13 of the Uniform Act adopted a year earlier), the Legislature required that the courts of this Commonwealth give the same effect to their own custody decrees as they had previously been required to give to decrees of courts in sister states.