Members of rival motorcycle gangs the Rock Machine and the Rebels were issued move on notices at a music festival in Perth on the weekend.
Police say members of the rival gangs had words during the Supafest concert at Joondalup Arena.
The men were issued with move-on notices and left the premises.
Tensions between the two gangs are high.
A member of the Rock Machine has been charged with the attempted shooting murder of Rebels state president Nick Martin.