At least 12 people have been barred from a security zone around the Land Forces weapons expo in Perth, prompting activists and Greens MP Sophie McNeill to threaten legal action.

The expo is due to begin on 6 October at the Perth Convention and Exhibition Centre. Police issued the exclusion orders using powers enacted by Western Australia last month. For 10 days, the zone covers the area between the convention centre and Elizabeth Quay bus port.

Activists Will Shanahan and Matilda Lane-Rose said they would take legal action unless police and police minister Reece Whitby reconsidered the bans. Lane-Rose said police had told her she was excluded even though she did not plan to attend the protest against the expo.

Anyone who breaches an exclusion order could face up to three years in prison and a $36,000 fine. Whitby said the powers were designed to prevent dangerous or disruptive behaviour and that each excluded person had a history of posing a serious threat to people or property.