An arrest warrant is an authorization issued to a law enforcement officer or agency by a judicial officer, allowing them to detain an individual suspected of a crime and bring him or her before the court. In the United States, the fourth amendment to the U.S. constitution and various state constitutions forbid law enforcement officers or agencies to make an arrest without a warrant, except in certain circumstances.
The fourth amendment to the U.S. Constitution safeguards the individual rights of citizens by protecting them from being arrested by a law enforcement officer or agency unjustly. To arrest an individual, the law enforcement officer or agency must receive an authorization from a judicial officer; this authorization is called an arrest warrant. In order to get an arrest warrant issued against an individual or group, the law enforcement officer or agency must demonstrate that there's probable cause that a crime was committed by the individual.