Va. Code § 18.2-411
When any number of persons, whether armed or not, are unlawfully or riotously assembled, the sheriff of the county and his deputies, the police officials of the county, city or town, and any assigned militia, or any of them, shall go among the persons assembled or as near to them as safety will permit and command them in the name of the Commonwealth immediately to disperse. If upon such command the persons unlawfully assembled do not disperse immediately, such sheriff, officer or militia may use such force as is reasonably necessary to disperse them and to arrest those who fail or refuse to disperse. To accomplish this end, the sheriff or other law-enforcement officer may request and use the assistance and services of private citizens. Every endeavor shall be used, both by such sheriff or other officers and by the officer commanding any other force, which can be made consistently with the preservation of life, to induce or force those unlawfully assembled to disperse before an attack is made upon those unlawfully assembled by which their lives may be endangered.
Va. Code § 18.2-411