The Queensland Police Union wants to buy the property where two officers were killed in the state's Western Downs last week.
Union president Ian Leavers said he did not want the land to "fall into the wrong hands".
"The last thing we want to see is the anti-vaxxers, pro-gun, conspiracy theorists to get this land and use it for their own warped and dangerous views," Mr Leavers said.
"They are absolutely un-Australian and I don't want it to be used for them to promote themselves.
"It is a sacred site for police and it's a way we can ensure their memory also lives on forever."
The Wieambilla property, near Tara, was the site of a major police investigation after two officers, constables Rachel McCrow and Matthew Arnold, and nearby resident, Alan Dare, were gunned down last week.
The three offenders responsible for the ambush, brothers Nathaniel and Gareth Train, and Gareth's wife Stacey Train, were all fatally shot by specialist police at the site.
Gareth had a YouTube channel, which has now been deleted, which contained many posts referencing COVID conspiracies, anti-vaccination and sovereign citizens.
The union said if it was successful the land would be repurposed so the legacies of Constables McCrow and Arnold could live on.
"What has been suggested to me by some police is this could not only become a memorial site for Matthew and Rachel," he said.
"But also, it could be used as a retreat for police who are doing it tough as well as it could be used for training purposes."
Mr Leavers said he had spoken to the families of the fallen officers about the proposal.
"This is a very emotional time for Matthew's and Rachel's families, and I have been talking with them, and they are really pleased," he said.
Mr Leavers said discussions had already begun with Premier Annastacia Palaszczuk.
A Queensland government spokesperson said the government was "committed to working with Mr Leavers, the Queensland Police Union and all parties to safeguard this land for the future and will respectfully consider the proposal".
Police Minister Mark Ryan said conversations were underway as to whether the government or the union would buy the site.
"In my view, that ground is now sacred ground. That is where the lives of two heroes of Queensland were taken," he said.
"The police union have put up a number of ideas.
"At the very least I think it should be also incorporating a memorial, a sacred space, to honour those heroes of Queensland."
