Different states have different laws. Here is Louisiana Revised Statutes on Riots.
Title 14 (State Statues)
§329.1. Riot
A riot is a public disturbance involving an assemblage of three or more persons acting together or in concert which by tumultuous and violent conduct, or the imminent threat of tumultuous and violent conduct, results in injury or damage to persons or property or creates a clear and present danger of injury or damage to persons or property.
329.2. Inciting to riot
Inciting to riot is the endeavor by any person to incite or procure any other person to create or participate in a riot.
329.3. Command to disperse; who may give; failure to comply
A. Any law enforcement or peace officer or public official responsible for keeping the peace may issue a command to disperse under the authority of R.S. 14:329.1 through 329.8 if he reasonably believes that riot is occurring or about to occur. The command to disperse shall be given in a manner reasonably calculated to be communicated to the assemblage.
B. Whoever willfully fails to comply with a lawful command to disperse shall be punished in accordance with the provisions of R.S. 14:329.7.
329.4. Wrongful use of public property; permits for use of public property
A. Wrongful use of public property is:
(1) The intentional entering of or onto any public property without the permission of the lawful custodian thereof, or his designated representative, at any time when the public property is not open to the public and the remaining in or occupying of any public property after having been requested to leave by the lawful custodian thereof, or his designated representative, or any law enforcement or peace officer, and
(2) The depriving of the general public of the intended use of public property without a permit.
D. For the purposes of this Section, the term "public property" means any public land, building, facility, structure, or enclosure used for a public purpose or as a place of public gathering, owned or under the control of the state or one of its agencies or political subdivisions.
329.7. Punishment
A. Whoever willfully is the offender or participates in a riot, or is guilty of inciting a riot, or who fails to comply with a lawful command to disperse, or who is guilty of wrongful use of public property, or violates any other provision hereof shall be fined not more than five hundred dollars or be imprisoned not more than six months, or both.
B. Where as a result of any willful violation of the provisions of R.S. 14:329.1-14:329.8 there is any serious bodily injury or any property damage in excess of five thousand dollars, such offender shall be imprisoned at hard labor for not more than five years.
C. Where, as a result of any willful violation of the provisions of R.S. 14:329.1-14:329.8, the death of any person occurs, such offender shall be imprisoned at hard labor for not to exceed twenty-one years.
14 (State Statues)
§329.1. Riot
A riot is a public disturbance involving an assemblage of three or more persons acting together or in concert which by tumultuous and violent conduct, or the imminent threat of tumultuous and violent conduct, results in injury or damage to persons or property or creates a clear and present danger of injury or damage to persons or property.
329.2. Inciting to riot
Inciting to riot is the endeavor by any person to incite or procure any other person to create or participate in a riot.
329.3. Command to disperse; who may give; failure to comply
A. Any law enforcement or peace officer or public official responsible for keeping the peace may issue a command to disperse under the authority of R.S. 14:329.1 through 329.8 if he reasonably believes that riot is occurring or about to occur. The command to disperse shall be given in a manner reasonably calculated to be communicated to the assemblage.
B. Whoever willfully fails to comply with a lawful command to disperse shall be punished in accordance with the provisions of R.S. 14:329.7.
329.4. Wrongful use of public property; permits for use of public property
A. Wrongful use of public property is:
(1) The intentional entering of or onto any public property without the permission of the lawful custodian thereof, or his designated representative, at any time when the public property is not open to the public and the remaining in or occupying of any public property after having been requested to leave by the lawful custodian thereof, or his designated representative, or any law enforcement or peace officer, and
(2) The depriving of the general public of the intended use of public property without a permit.
D. For the purposes of this Section, the term "public property" means any public land, building, facility, structure, or enclosure used for a public purpose or as a place of public gathering, owned or under the control of the state or one of its agencies or political subdivisions.
329.7. Punishment
A. Whoever willfully is the offender or participates in a riot, or is guilty of inciting a riot, or who fails to comply with a lawful command to disperse, or who is guilty of wrongful use of public property, or violates any other provision hereof shall be fined not more than five hundred dollars or be imprisoned not more than six months, or both.
B. Where as a result of any willful violation of the provisions of R.S. 14:329.1-14:329.8 there is any serious bodily injury or any property damage in excess of five thousand dollars, such offender shall be imprisoned at hard labor for not more than five years.
C. Where, as a result of any willful violation of the provisions of R.S. 14:329.1-14:329.8, the death of any person occurs, such offender shall be imprisoned at hard labor for not to exceed twenty-one years.