Classification of laws in force

Though a number of classifications are possible, the most useful categories are (1) substantive and procedural, (2) public and private, and (3) civil and criminal.

Basic to understanding these classifications are the terms right and duty.A right is the capacity of a person, with the aid of the law, to require another person or persons to perform, or to refrain from performing, a certain act. Thus, if A sells and delivers goods to B for the agreed price of $100 payable at a certain date, A has the capability, with the aid of the courts, of enforcing the payment by B of the $500. A duty is the obligation the law imposes upon a person to perform, or to refrain from performing, a certain act. Duty and right are correlatives: no right can rest upon one person without a corresponding duty resting upon some other person or, in some cases, upon all other persons.

SUBSTANTIVE AND PROCEDURAL LAW
Substantive law creates, defines, and regulates legal rights and duties. Thus, the rules of contract law that determine when a binding contract is formed are rules of substantive law. This book is principally concerned with substantive law. 

On the other hand, procedural law establishes the rules for enforcing those rights that exist by reason of substantive law. Thus, procedural law defines the method by which one may obtain a remedy in court.
 

PUBLIC AND PRIVATE LAW
Public law is the branch of substantive law that deals with the government’s rights and powers in its political or sovereign capacity and in its relation to individuals or groups.Public law consists of constitutional, administrative, and criminal law. Private law is that part of substantive law governing individuals and legal entities (such as corporations) in their relations with one another. Business law is primarily private law.

CIVIL AND CRIMINAL LAW
The civil law defines duties the violation of which constitutes a wrong against the party injured by the violation. In contrast, the criminal law establishes duties the violation of which is a wrong against the whole community. Civil law is a part of private law, whereas criminal law is a part of public law. Civil law should be distinguished from the concept of a civil law system. In a civil action the injured party sues to recover compensation for the damage and injury he has sustained as a result of the defendant’s wrongful conduct. The party bringing a civil action has the burden of proof, which he must sustain by a preponderance of the evidence. Whereas the purpose of criminal law is to punish the wrongdoer, the purpose of civil law is to compensate the injured party. The principal forms of relief the civil law provides are a judgment for money damages and a decree ordering the defendant to perform a specified act or to desist from specified conduct.