Police were pelted with rocks and bottles at an out of control party in Mandurah overnight.
Officers were forced to don riot gear as they tried to break up the gathering of about 120 young people at the Cassilis Court house.
Twenty police vehicles and a helicopter were sent to the party at 9:30pm.
A 48-year-old man has been charged with obstructing police and a 19-year-old man has been charged with disorderly conduct.
Inspector Neil Blair says the incident highlights a lack of respect toward police officers.
“It is disappointing that young people continue to consume alcohol, act in a disorderly manner, with absolutely no respect for police, nor any regard how it affects people living in that community,” he said.
“One would question what parental supervision is in play and what responsibility party organisers believe they should accept.”
No-one was injured during the incident.