be so substantial that there are reasonable grounds to believe that such claim is correct. In the said case, the proof adduced by the respondent therein was so substantial and conclusive as to his citizenship that it warranted a judicial intervention. In the present case, there is a substantial or conclusive evidence that petitioners are Filipino citizens. Without necessarily judging the case on its merits, as to whether petitioners had lost their Filipino citizenship by having a Canadian passport, the fact still remains, through the evidence adduced and undisputed by the respondents, that they are naturalized Filipinos, unless proven otherwise. However, this Court cannot pass upon the issue of petitioners' citizenship as this was not raised as an issue. The issue in this petition is on the matter of jurisdiction, and as discussed above, the trial court has jurisdiction to pass upon the issue whether petitioners have abandoned their Filipino citizenship or have acquired dual citizenship within the confines of the law.   In this regard, it must be remembered though that this Court's ruling in Dwikarna v. Domingo did not abandon the doctrine laid down in BOC v. Dela Rosa. The exception remains. Dwikarna merely reiterated the doctrine of primary jurisdiction when this Court ruled that if the petitioner is dissatisfied with the decision of the Board of Commissioners of the Bureau of Immigration, he can move for its reconsideration and if his motion is denied, then he can elevate his case by way of a petition for review before the Court of Appeals, pursuant to Section 1, Rule 43 of the Rules of Civil Procedure. However, utmost caution must be exercised in availing of the exception laid down in BOC v. Dela Rosa in order to avoid trampling on the time-honored doctrine of primary jurisdiction. The court cannot or will not determine a controversy involving a question which is