Section 19. (1) Excessive fines shall not be imposed, nor cruel, degrading or inhuman punishment inflicted. Neither shall death penalty be imposed, unless, for compelling reasons involving heinous crimes, the Congress hereafter provides for it. Any death penalty already imposed shall be reduced to reclusion perpetua. (2) The employment of physical, psychological, or degrading punishment against any prisoner or detainee or the use of substandard or inadequate penal facilities under subhuman conditions shall be dealt with by law. Section 20. No person shall be imprisoned for debt or non-payment of a poll tax. Section 21. No person shall be twice put in jeopardy of punishment for the same offense. If an act is punished by a law and an ordinance, conviction or acquittal under either shall constitute a bar to another prosecution for the same act. Section 22. No ex post facto law or bill of attainder shall be enacted. ARTICLE IV CITIZENSHIP Section 1. The following are citizens of the Philippines: [1] Those who are citizens of the Philippines at the time of the adoption of this Constitution; [2] Those whose fathers or mothers are citizens of the Philippines; [3] Those born before January 17, 1973, of Filipino mothers, who elect Philippine citizenship upon reaching the age of majority; and [4] Those who are naturalized in accordance with law. Section 2. Natural-born citizens are those who are citizens of the Philippines from birth without having to perform any act to acquire or perfect their Philippine citizenship. Those who elect Philippine citizenship in accordance with paragraph (3), Section 1 hereof shall be deemed natural-born citizens. Section 3. Philippine citizenship may be lost or reacquired in the manner provided by law. Section 4. Citizens of the Philippines who marry aliens shall retain their citizenship, unless by their act or omission, they are deemed, under the law, to have renounced it. Section 5. Dual allegiance of citizens is inimical to the national interest and shall be dealt with by law.