CONSTITUTIONAL LIMITATIONS
1. DUE PROCESS OF LAW
       There must be a valid law
       Tax measure should not be unconscionable and unjust as to amount to confiscation of
        property.
       Tax statute must not be arbitrary as to find no support in the Constitution.
Sec. 1 Art. III 1987 - No person shall be deprived of life, liberty, or property without due process of
law, nor shall any person be denied the equal protection of the laws.
Sison v. Ancheta, supra – BP 135
FACTS: Batas Pambansa 135 was enacted. Sison, as taxpayer, alleged that its provision (Section 1)
unduly discriminated against him by the imposition of higher rates upon his income as a professional,
that it amounts to class legislation, and that it transgresses against the equal protection and due
process clauses of the Constitution as well as the rule requiring uniformity in taxation.
Issue: Whether BP 135 violates the due process and equal protection clauses, and the rule on
uniformity in taxation.
HELD:     No, there was no violation of the due process and equal protection clause, since petitioner
did not made a case, only allegations.
       The Congress has the power to determine the rates of taxation; thus,  the due process clause
        may be invoked where a taxing statute is so arbitrary that it finds no support in the
        Constitution. An obvious example is where it can be shown to amount to the confiscation of
        property. That would be a clear abuse of power. It then becomes the duty of this Court to say
        that such an arbitrary act amounted to the exercise of an authority not conferred. That
        properly calls for the application of the Holmes dictum.
       It has also been held that where the assailed tax measure is beyond the jurisdiction of the
        state, or is not for a public purpose, or, in case of a retroactive statute is so harsh and
        unreasonable, it is subject to attack on due process grounds.