Legal bibliography principles classify authorities as primary and secondary. Again, using Moreno's tract:
1. An authority is considered primary when legislation (or statutes) or court decisions are involved.
Primary authorities are either mandatory or persuasive.
a. It is mandatory when "legislation is effective in the place where it has been enacted or promulgated or when a decision is rendered with finality by a superior court in the case or in another case with a similar set of facts, or by the same court in another case."
b. Any other type of legislation or court decision is considered persuasive.
2. An authority is considered secondary, "when primary authority is commented on, criticized, explained or restated."
Here are the basic principles of Philippine legal bibliography:
I. Not all legal authorities are created equal.
II. Some authorities are considered primary, while others, only secondary.
III. The following is a practitioner's take on the Hierarchy of Authorities --
(i) The Constitution
(ii) Statutes proper, treaties
(iii) Municipal legislation
(iv) Administrative rules issued pursuant to law.
2. Decisions of the Supreme Court
3. Other types of administrative rules
4. Decisions of other courts and quasi-judicial bodies
5. Opinions of government agencies tasked with administering particular laws
6. Foreign laws and cases
B. Secondary Authorities
1. Local commentaries
2. Local textbooks
3. Local legal dictionaries
4. Local legal articles
5. Foreign secondary authorities [may rank higher in certain cases]
IV. This hierarchical order is a general concept. You need to test each possible authority for relevance and applicableness. If an authority is not relevant or applicable to your problem or case, it must fall away.
V. When considering a secondary authority, pay attention to the subject matter of the material, the year it was published, and the author. Certain commentaries, because of usage, time and the reputation of their authors are considered "repositories of law" and may carry greater weight than other commentaries.
VI. The Hierarchy of Authorities is your best friend.