Presumption of constitutionality of laws

"Because all laws enjoy the presumption of constitutionality, courts will uphold a law’s validity if any set of facts may be conceived to sustain it.87 On its face, we find that there are at least two conceivable bases to sustain the subject regulation’s validity absent clear and convincing proof that it is unreasonable, oppressive or confiscatory. Congress may have legitimately concluded that
business establishments have the capacity to absorb a decrease in profits or income/gross sales due to the 20% discount without substantially affecting the reasonable rate of return on their investments considering (1) not all customers of a business establishment are senior citizens and (2) the level of its profit margins on goods and services offered to the general public. Concurrently, Congress may have, likewise, legitimately concluded that the establishments, which will be required to extend the 20% discount, have the capacity to revise their pricing strategy so that whatever reduction in profits or income/gross sales that they may
sustain because of sales to senior citizens, can be recouped through higher markups or from other products not subject of discounts. As a result, the discounts resulting from sales to senior citizens will not be confiscatory or unduly oppressive.

In sum, we sustain our ruling in Carlos Superdrug Corporation88 that the 20% senior citizen discount and tax deduction scheme are valid exercises of police power of the State absent a clear showing that it is arbitrary, oppressive or confiscatory."