(c) The principle given above is to be understood of the taking effect of a law, for the continuance of a law may depend on the acceptance of the people in the sense that a contrary custom of the people is able to abrogate law, if the superior consents (see 500 sqq.). Few codes of modern states give legal force to popular custom; they suppose that, if a law is not satisfactory to the people, the way is open to its repeal through exercise of the suffrage. But, morally speaking, there is no obligation to obey a law that has fallen into desuetude.
545. As to laws made by one who has no lawful authority, we should note: (a) of themselves, they have no binding force, since law is an act of authority; (b) from the necessities of the case, they are obligatory, if, being otherwise just, they are accepted by the great body of the people; for to resist them then would be prejudicial to public order.
546. Subject-Matter.—The objects or classes of temporal goods that fall under the regulation of civil law are many:
(a) external goods, or goods of fortune, which should have the protection of the State; and the laws regarding them should promote agriculture, commerce, industry, the arts, etc.;
(b) the goods of the body, which are more important still, and hence the law should favor the family and the increase of its members, and should provide for the health and well-being of the citizens by sanitary regulations and measures of relief for the needy, the unemployed, the orphans, and the aged;
(c) the goods of the mind, which are necessary for progress and happiness, and hence the law should provide the means for instruction in the secular arts and sciences and for the general diffusion of useful knowledge;
(d) the goods of the will (i.e., virtue and morality), which are most important both to the individual and the community, and hence the law must safeguard public decency and sobriety, and restrain and punish the opposite crimes and vices;
(e) the social goods of the people, which are promoted by wise legislation concerning the form and administration of government, the mutual duties and rights of citizens, the protection of the State and of its members, etc.
547. The relation of civil law to natural law is as follows:
(a) The State has no power to make laws that are opposed to nature, for, since law is an ordinance according to reason, any human command that is contrary to nature and therefore to reason is not law, but the corruption of law. No sin, not even a venial sin, can be made obligatory by law. Example: The rule of Sparta that sickly infants were to be put to death was not law but legalized murder.