A more thorough explanation:

Definition: Fons juris is a Latin term that means "source of law." It refers to something that provides authority for legislation and judicial decisions. It is the point of origin for law or legal analysis.

For example, a constitution, treaty, statute, or custom can be a fons juris. These sources of law provide the basis for legal decisions and actions. They are the starting point for legal analysis and interpretation.

When judges make decisions, they draw upon various sources of law, such as statutes, judicial precedents, custom, the opinion of experts, morality, and equity. These sources of law help judges determine the rules by which to decide cases.

Legal researchers also use sources of law to find information about the law. They may consult books, computer databases, microforms, optical disks, and other media that contain legal information. These sources of law help researchers understand the law and its applications.

In summary, fons juris refers to the sources of law that provide the basis for legal decisions and actions. These sources of law are essential for legal analysis and interpretation.