Western Australian police can search people's bags and vehicles for 10 days from Thursday, leading up to Land Forces 2026, Australia's largest land defence industry exhibition which runs from October 6 to 8 in Perth.
The temporary powers also enable officers to establish checkpoints, cordons, and roadblocks, and issue lawful directions for 10 days in the city.
Police may also seize prohibited items deemed to be a safety risk or potentially used to disrupt the event. Homeless people will be moved on.
People who fail to comply with lawful directions could be refused entry to the event precinct or ordered to leave.
"This is a heightened security environment, and what we want to see is this event occur safely," WA Police Minister Reece Whitby told reporters.
"We will not tolerate what occurred in Melbourne at the last Land Forces ... where horses were splashed, and police were splashed with urine and acid, and ball bearings were thrown under the hooves of police horses, and there were fires started, and punches thrown."
Thousands of interstate and international delegates are expected to attend the event, including high-ranking government and military officials.
Minister Whitby rejected claims the legislation giving police extra powers was "anti-protest".
"If you're a protester, and you want to voice your thoughts against this event, we will allow that," he said.
"We will make sure that you're protected and safe when you do so."
Using their bolstered powers, WA police have already banned multiple people from the conference security zone.
A police spokesman declined to provide details on the number of people excluded from the event, but said they had "earned it through previous suboptimal behaviour".
"If someone is excluded, they have sufficient behavioural problems, and some of that includes criminal histories," the senior officer said.
Officers will use facial recognition technology to enforce bans.
WA Greens MLC Sophie McNeill said the Land Forces laws were being used to crack down on peaceful protesters.
"This event is going to be hosting some of the most evil companies, some of the largest weapons manufacturers in the world who've been banned from other jurisdictions," she said.
"They've sent at least six letters that we know of to people who have no history of any violent offences, peaceful climate activists.
"It's complete overreach."
Anti-war, Palestine solidarity and environmental groups will protest against Land Forces on Tuesday in Perth city centre.
The powers were last used during the 2011 Commonwealth Heads of Government Meeting in Perth.
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