When is it okay to delegate powers?

The general rule is non-delegation of powers. The rule, however, which forbids the delegation of legislative power is not absolute and inflexible. It admits of exceptions. An exception sanctioned by immemorial practice permits the central legislative body to delegate legislative powers to local authorities. (G.R. No. L-45685; November 16, 1937)

"It is a cardinal principle of our system of government, that local affairs shall be managed by local authorities, and general affairs by the central authority; and hence while the rule is also fundamental that the power to make laws cannot be delegated, the creation of municipalities exercising local self government has never been held to trench upon that rule. Such legislation is not regarded as a transfer of general legislative power, but rather as the grant of the authority to prescribe local regulations, according to immemorial practice, subject of course to the interposition of the superior in cases of necessity." On quite the same principle, Congress is empowered to delegate legislative power to such agencies in the territories of the United States as it may select. A territory stands in the same relation to Congress as a municipality or city to the state government.
Courts have also sustained the delegation of legislative power to the people at large. Some authorities maintain that this may not be done. However, the question of whether or not a state has ceased to be republican in form because of its adoption of the initiative and referendum has been held not to be a judicial but a political question, and as the constitutionality of such laws has been looked upon with favor by certain progressive courts, the sting of the decisions of the more conservative courts has been pretty well drawn. Doubtless, also, legislative power may be delegated by the Constitution itself. Section 14, paragraph 2, of article VI of the Constitution of the Philippines provides that "The National Assembly may by law authorize the President, subject to such limitations and restrictions as it may impose, to fix within specified limits, tariff rates, import or export quotas, and tonnage and wharfage dues." And section 16 of the same article of the Constitution provides that "In times of war or other national emergency, the National Assembly may by law authorize the President, for a limited period and subject to such restrictions as it may prescribe, to promulgate rules and regulations to carry out a declared national policy." (G.R. No. L-45685; November 16, 1937)

It is beyond the scope of this decision to determine whether or not, in the absence of the foregoing constitutional provisions, the President could be authorized to exercise the powers thereby vested in him. Upon the other hand, whatever doubt may have existed has been removed by the Constitution itself. (G.R. No. L-45685; November 16, 1937)