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Legal Research

Fundamentals of Legal Research

Legal authority

What is "authority"?

Legal authorities are published sources of law that present legal rules, legal doctrine, or legal reasoning. Mersky & Dunn, Fundamentals of Legal Research (2002) at 2.

Legal authority refers to

(1) types of legal sources: primary or secondary, and

(2) the persuasiveness of legal information: binding or not.

Not all sources are given equal weight in court.

Primary v Secondary Authority

Often called primary or secondary sources

What's the difference?

Primary authority is actual law (statutes, cases, regulations, etc.).

Secondary sources are writings about the law (treatises, hornbooks, law review articles, etc.).


Primary Authority

Remember, law is generated by the three branches of government (judicial, legislative, executive) AND there are multiple levels of government (federal, state, local, and international). All laws of whatever sort from whatever branch and level of government are primary sources.

Finding primary authority is the ultimate goal of all legal research since you need to CITE SOME LAW to support your legal argument or opinion.


Secondary Authority

Secondary authority is any type of writing about primary authority.

Examples of secondary sources:

  • Treatises
  • Law review articles
  • Hornbooks
  • Practice guides
  • Form books
  • Websites
  • Restatements of the Law
  • Model codes

Uses of secondary authority:

  • Explain the law - this includes headnotes and other editorial additions to law books!
  • Cite to primary authority
  • May present novel theories that later find their way into primary authority
  • Often the best starting point for research, especially if you are unfamiliar with the area of law

Secondary sources are never binding authority. Generally you would NOT cite secondary authority in motions and briefs!

Mandatory v Persuasive Authority

Mandatory (or binding) authority

is the law of your jurisdiction. Only primary sources can be mandatory but not all primary sources are binding. Can you explain why?

Courts generally are supposed to follow the mandatory authority of the jurisdiction in which it sits. Otherwise, a court needs to explain why it declines to do so. Not following mandatory jurisdiction will likely lead to getting overturned on appeal!

Mandatory authority for a state law issue in Maine:

  • Maine constitution
  • Maine statutes
  • Maine Supreme Court decisions
  • Maine regulations

Example:  Recreational marijuana is allowed in some jurisdictions but not others. What is the law in Maine? Think about going into court arguing that your client is entitled to grow marijuana based on a Colorado law if the law was rejected by the Maine legislature ...

You can argue against mandatory authority in your jurisdiction, but remember Rule 11 sanctions:

When you sign a pleading, the legal argument needs to be “well grounded in fact and is warranted by existing law or a good faith argument for the extension, modification, or reversal of existing law…”


Persuasive authority

is authority (that is not mandatory) that is used to attempt to persuade a court when -

  • there is no relevant mandatory authority in a jurisdiction to resolve a legal issue, OR
  • you want to argue against application of the current law (i.e. mandatory authority) to resolve an issue (remember it must be a good faith argument)

Persuasive authority examples for a state law issue in Maine:

  • Federal court decisions interpreting Maine law
  • High court decisions of nearby states such as New Hampshire, Massachusetts or Vermont
  • High court decisions of other states in the 1st Circuit
  • Some states are more persuasive that others for a particular area of law (Delaware for corporate law questions)
  • Well respected secondary sources (Restatements on Torts, Dobbs on Torts)