This case is a special civil action for certiorari and prohibition, with a prayer for the issuance of a writ of preliminary injunction, seeking to annul an order is­sued by the respondent Judge on March 10, 1970 in Special Proceeding No. U-316 of the Court of First Instance of Pangasinan, Branch IX; to restrain all the respondents from implementing or executing said order, and lastly, to enjoin the private respondent from representing him­self as, or claiming to be a Filipino citizen, and from exercising rights and prerogatives as such.  The petition was grounded on the claim that the respondent Judge, in issuing the aforesaid order, acted without or in excess of his jurisdiction or with grave abuse of discretion.

On July 1, 1970, this Court issued a writ of pre­liminary injunction as prayed for in the petition.

Within the reglementary period the private respond­ent filed his answer to the petition in which he admitted some of the allegations made therein and denied the others.  By way of affirmative defense he averred that, under the Rules of Court and established jurisprudence, courts of general jurisdiction like the Courts of First Instance have jurisdiction over cases involving interpretation of the provisions of the Constitution; that a Court of First Instance is competent to decide whether or not a party is a citizen under the Treaty of Paris and/or the Philippine Bill of 1902, irrespective of whether this is the main issue in the proceeding or is only an incidental question therein; that the absence of a proceeding established by law or the rules for the declaration of citizenship of an individual does not mean that no such declaration may be made by the courts.

At the hearing of the case held on August 24, 1970, the court granted the parties a period of twenty days from that date to submit, simultaneously, their respective memo­randum.  After both parties had submitted such memoranda the case was deemed submitted for decision.

On March 19, 1971 the private respondent, through counsel, filed a motion, with the conformity of the Office of the Solicitor General, praying for the reasons therein set forth, "that an order be issued by this Honorable Court setting aside the decision of the Court of First Instance of Pangasinandeclaring respondent, Yu Lan alias Dy Kiana, as citizen of the Philippines," the same being null and void on jurisdictional grounds.

WHEREFORE as, prayed for, it is hereby ordered that the decision subject of the petition for certiorari and prohibition filed in this case be, as it is hereby set aside, and declared of no legal effect.

Without costs.

Concepcion, C.J., Reyes, J.B.L., Makalintal, Zaldivar, Ruiz Castro, Fernando, Teehankee, Barredo, Villamor, and Makasiar, JJ., concur.