In essence, primary sources are the law. Primary sources originate from the executive, judicial, and legislative branches of government. Primary sources are classified as the following: case law, administrative law, federal or state statutes, state constitutions or the U.S. Constitution.

Primary sources are important to legal research because primary sources are the rules of law that must be followed.

Secondary sources are about the law. Secondary sources provide an overview and analysis of laws or subject areas of law. Secondary sources can be utilized in legal research as a shortcut for locating the correct legal authority. Secondary sources are never binding, but can be persuasive. 

Primary sources are only considered the legal authority when the primary sources are binding upon the court. Law is considered binding when the court is legally required to follow it. Primary sources are also known as "binding primary authority" when they are binding. Basically, case law, administrative law, federal and state statutes, state constitutions and the U.S. Constitution can all be binding on a court.

Law is only binding when the jurisdiction and level of government are the same for the primary source and the legal issue. In short, federal courts are binding on other federal courts when they are applying federal law, and state courts are binding on the courts within the same state when they are applying state law. For example, a state precedent case has no authority in a federal court unless the legal issue requires the federal court to apply the state's law to the case. If there are federal laws on an issue, the federal laws will always have authority higher than the state laws which is known as preemption.

Federal:

• The U.S. Supreme Court is binding upon all issues of federal law in every type of court.
  • Only the U.S. Supreme Court is binding upon state courts for issues of federal law.
• The U.S. Court of Appeals is only binding upon district courts within the same circuit.
• The U.S. district courts are not binding upon any court.

State:

• State courts are only binding on courts within the same state.
• The supreme court in the state is binding upon all courts in the state.
• The state's appeals court is binding only on the state's trial courts.
• The state's trial courts are not binding.

Primary sources can be utilized in legal documents for persuasion, if they are not legally binding, but the court does not have to follow these like binding primary authority. Instead, primary sources can be utilized to persuade the court to rule in a certain way. Non-binding legal authority should never be used to explain the law.

Make sure the law is good law!

The history and the precedential value of a case needs to be determined before relying upon it! Some decisions are later either criticized, overruled, or reversed. Relying upon case law with a negative treatment is basically relying on bad law. Cases can also be analyzed through the citation history of a case based upon how it is treated. It is important to note that some cases may be only overruled or reversed in part, and could still have some precedential value.

The CRAAP test can be applied to a legal secondary sources to analysis the source.

How to use the CRAAP test with secondary sources?

• For currency, it needs to be determined if the law is good law. This involves looking at the date of the source, and determining if the primary authority has been amended, repealed, overruled, or otherwise changed since the source was published. Recent developments and settled areas of law have different currency standards.
• For relevance, the main question is if it is focused upon the correct law. Reading through the source and reviewing the citations can help determine this.
• For authority, the focus is upon the subject area and jurisdiction. This will determine if the source cites to the correct authority.
• For accuracy, focus on affiliations: the credentials of the publisher or author of the secondary source. The reputation of the database and location of where it was published also matters significantly. 
• For purpose, the audience is crucial. The reason the source was written and the intended legal audience can help determine if the source purpose is related to the reason for the legal research. For example, the Nutshell books are intended for legal audiences in each subject area that want to know more about that area of law.